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LS1 Rear Mid-Engine AWD (C5 Corvette donor)

Old 05-10-2013, 02:22 PM
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Default LS1 Rear Mid-Engine AWD (C5 Corvette donor)

I know some of you may be breathing a sigh as you read this. Another Corvette AWD dreamer? Not exactly. Don't get me wrong, I am a dreamer but just of a different kind.

I am in the research phase for a fun project that I could definitely use some advice on. I plan to build a custom Lamborghini Murcielago LP640 replica using a C5 as the primary donor. I plan to use as much from the C5 as possible to keep the costs as low as possible. As you may know, the Murci is a rear mid-engine AWD vehicle. I am not trying to reproduce the exact HP or anything but I thought it would be fun to make an AWD replica since there haven't been many (any?) done - maybe that should tell me something.

I have searched the forum and found several related threads but I couldn't find anything close enough that has actually been completed. If any of you know of a similar project that has been completed, I'd love to be pointed to it.

Before any of you say, "why would you want AWD", save it. The gas mileage difference is negligible and it would just be cool to do. Simple as that.

I will say this up-front, my brother is the experienced mechanic and fabricator - not me - and he will be helping me with this build. I am just doing some leg work to see what options may be available. So, if I get some technical stuff wrong or say something that simply isn't possible, please let me know but be patient with me.

So on to the details...This car will be built on a custom chassis so the main limit is everything has to fit below the body I will be putting on it. Again, I plan to harvest EVERYTHING I can from a C5 donor. I definitely want to use the power steering, suspension, LS1 and I'd like to use the 4L60-E tranny if possible too. I may be convinced to upgrade to the 4L65-E or even 4L80-E if the benefits vs. cost was there. Who knows, I may want to build the engine someday and it would be nice to know the car was ready for it.

I had a couple ideas for the AWD set-up but I am not decided on anything yet. All ideas include flipping the front/rear so I can mount the engine in the rear. Some of those ideas include:

1) Use a Haldex system like what is in the Buick LaCrosse & Cadillac SRX - not really sure what would be involved in this
2) Use a GMC Syclone/Typhoon AWD set-up
3) Use a Chevy Astro van set-up

My idea is to mount the engine/tranny so the tranny runs between the seats like on a real lambo, run one drive shaft from the t-case under the engine to an offset rear diff while running the other shaft to the front diff.

Some of the problems I have already thought of that need addressing:

1) As I understand it, the t-case power split will likely be rear-biased which once flipped the other way will become front-biased. I haven't asked my brother how to overcome this yet. I'd love any ideas.
2) Running the driveshaft under the engine may require the engine to sit too high to make this work.

Looking forward to some feedback/advice. I'd love to hear better ideas if anyone has them.

Mike
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Old 05-10-2013, 04:09 PM
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its a good idea in theory but I dont think it would work..I mean I would love to take something like a slc kit car and make it awd but I just dont think its possible..
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Old 05-10-2013, 04:20 PM
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Maybe not. I'm here to get educated.

Why don't you think it will work? What are your reasons?

Mike
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Old 05-10-2013, 07:36 PM
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I don't think you will be able to fit a LS1 anywhere near the back or middle of a Corvette chassis. I also dont believe that the chassis was designed to carry the weight of the motor in the back.

I might look at a platform that is already mid/rear and start from there. Unfortunately most of those platforms are exotics (Ferrari, Lambo) or too small (Fiero, MR2).

I like the idea, but the point of mid/rear engines was for weight distribution and the Corvette is already at 50/50 front to rear.

I think you should try a base Corvette, but try and rig up an AWD system. Moving the motor to the back/middle doesn't sound possible with a Vette...
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Old 05-10-2013, 07:56 PM
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While I applaud your motivation but I just cant begin to tell you how big of project this is going to be. Im not here to bash you or tell you its a bad idea, its just a way bigger of project than you can imagine.

I personally (by myself) built from scratch a Lambo Diablo Roadster replica and just finished swapping out the sbc/5 speed with a LS4 drivetrain so I have somewhat of a idea what your up against.

First - just completing any Lambo based replica is almost impossible for someone who doesnt personally have a strong skill set in welding and fiberglass/paint work and a large investment of tools and a good working space. Someone like yourself who will have to depend alot on someone else's skills and schedule (i.e.freetime) to help you with your project will greatly slow down your build. There is just so much to do on these replicas either on a donor chassis or even more on a custom tube chassis. It would take what would seem like forever just to get a rolling chassis and even more important money... Which brings me to;

Second- The money.... In your head right now it seems very doable, a little money here a little money there and its done.... For the type of build your thinking about can reach $70k-$80k very easy, and yes even if you have a donor. And thats alot of money for something "cool". An what happens in alot of cases people will start out and dump out $20k for a replica kit, a donor, some metal and maybe some glass or interior pieces and not even be 5% done. The way these things work is something always comes up in these builds, lose a job, family issues, health, wives, girlfriends, (sometimes both) ect, ect. Then 2 or 3 years later you figure out your going to need another $40k to finish and another year or two after that you now need another $10k for tires/wheels/paint/ect and that seems to unmotivate alot of people and they end up selling the whole unfinished project for $4000.00 on craigslist....

Sadly this is situation for 90% of replica builds or you pay a bunch of money to some "professional" and they take your money and run... Which brings me to #3-

Third- The replica industry is plagued with scammers, you know scum of the earth people. Im not only talking about builders but suppliers as well, there are very few people out there selling quailty replica kits and parts.

Fourth- Now lets just only consider your awd concept, if you really truley think you can over come all the above issues and still want to continue- (knowing your going to have to spend thousands and thousands of dollars and spend thousands of hours building this project) your going to have to consult with a master fab/chassis/cad person to design this chassis. Its not something a normal guy that can weld and work on cars can do, there is a design process that has to be done when you build something like this. You just cant take this chassis or that chassis ad cut it up, mount the engine in the middle somewhere and be done. Its got to be safe and function correctly.

I dont want to bash anyone here on this forum but this might not be place you want to get advice from. For something like this that hasnt been done before and this technical you dont want to risk your life and/or someone elses driving this thing on the road.

In closing, Im not trying to bash you in anyway, maybe just prepping you for whats ahead. My advice- Find someone elses' unfinished replica project and keep it simple. If you have to swap in a LS4, 3800s/c or even a LS with a Porsche trans. Just keep your build goals realistic. If you plan well enough(and keep it simple) there is no reason you cant have a good looking replica for $30k-$40k and have it done in a year or so. Being able to have a nice looking running/driving replica is plently cool enough.
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Old 05-10-2013, 08:04 PM
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gun5l1ng3r, I didn't mean to imply that I was planning to relocate the LS1 to the rear of the Corvette chassis - no way that would work for all the reasons you stated. I mentioned in the first post that this would be built on a custom chassis. It will be an exotic replica with most of the parts coming from a C5!
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Old 05-10-2013, 08:41 PM
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tonypaul,

Small world! I recognize you from lamboclone.com where I am also an active member. You have a beautiful car! I also saw the threads on your own engine/tranny adventures.

Your points are valid. Based on your experience, your insight is valuable and I will definitely take it into consideration.

I understand this is a big project. I also am willing to admit it is probably even larger than I can comprehend at this point.

I think I am being realistic about the time and money this will take. I am also not in a hurry. I am in for the long haul (several years). I don't care if it takes 10 years - and it might! Worst case scenario, if all goes bad and I become disabled and bail on my plan to build the car and sell it before it is finished, that isn't the worst thing in the world either - but I don't think that is going to happen. My brother and I both have a strong interest in this and we will get it done.

I also know all about the scammers. I don't know why this hobby has so many of them but it does seem to.

I could be wrong but it sort of seems like you are a little annoyed that someone who you don't deem to have the resources and skill to pull off a project like this (someone without your chops) would even consider it. But you don't know me or how driven I am. I am here to learn and make decisions. I have all the time in the world to get this right.

The only thing you have said so far that even gives me pause is regarding the chassis. I understand and agree with proper design and safety. I guess I don't understand why a modified NAERC or Chassisworks design can't be used. These are proven designs that are generally believed to be relatively safe and people are using them every day. What makes AWD so special that it will require something unobtainable? That is not a rhetorical question. I would love to know exactly what I am up against. I'd be very interested to hear about your chassis and why AWD would not work on it.

I disagree that this isn't the forum for this question. This question is not about building a replica kit. The question is about the technical feasibility of putting together a custom rear mid-engine AWD vehicle. Forget I mentioned it was a Murcielago replica for a minute.

What are the technical hurdles and challenges I will encounter as a result of trying to flip an existing AWD system to be used in a mid-engine design and can those be overcome? Hey, if they can't be overcome, I will move on with a set-up similar to yours - I'm certain it is very nice.

Mike

Last edited by BigPines; 05-10-2013 at 08:51 PM.
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Old 05-10-2013, 11:16 PM
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Originally Posted by BigPines View Post
tonypaul,

Small world! I recognize you from lamboclone.com where I am also an active member. You have a beautiful car! I also saw the threads on your own engine/tranny adventures.

Your points are valid. Based on your experience, your insight is valuable and I will definitely take it into consideration.

I understand this is a big project. I also am willing to admit it is probably even larger than I can comprehend at this point.

I think I am being realistic about the time and money this will take. I am also not in a hurry. I am in for the long haul (several years). I don't care if it takes 10 years - and it might! Worst case scenario, if all goes bad and I become disabled and bail on my plan to build the car and sell it before it is finished, that isn't the worst thing in the world either - but I don't think that is going to happen. My brother and I both have a strong interest in this and we will get it done.

I also know all about the scammers. I don't know why this hobby has so many of them but it does seem to.

I could be wrong but it sort of seems like you are a little annoyed that someone who you don't deem to have the resources and skill to pull off a project like this (someone without your chops) would even consider it. But you don't know me or how driven I am. I am here to learn and make decisions. I have all the time in the world to get this right.

The only thing you have said so far that even gives me pause is regarding the chassis. I understand and agree with proper design and safety. I guess I don't understand why a modified NAERC or Chassisworks design can't be used. These are proven designs that are generally believed to be relatively safe and people are using them every day. What makes AWD so special that it will require something unobtainable? That is not a rhetorical question. I would love to know exactly what I am up against. I'd be very interested to hear about your chassis and why AWD would not work on it.

I disagree that this isn't the forum for this question. This question is not about building a replica kit. The question is about the technical feasibility of putting together a custom rear mid-engine AWD vehicle. Forget I mentioned it was a Murcielago replica for a minute.

What are the technical hurdles and challenges I will encounter as a result of trying to flip an existing AWD system to be used in a mid-engine design and can those be overcome? Hey, if they can't be overcome, I will move on with a set-up similar to yours - I'm certain it is very nice.

Mike
It dont bother me personally that people with less skill sets want to take on such projects, but it just makes me feel bad to see people loose motivation and are not able to complete their projects and end up in a bad situation. Theres alot of people out there (not you) that think building a replica is like adding a body kit and can be done in a couple weekends. I dont have that great of skill set, in fact 6 or 7 years ago I purchased a ferrari kit and got in over my head with it. Lack of money and lack of experience led me to sell it at a major loss. So I know first hand.

The only way to get experience is to get busy and get your hands dirty. And its really great that you have that motivation and I see now you have been doing the right research on what to expect. Im one of those guys who enjoys the build and the challangelearning more than the finished project. I have built 5 or 6 projects only to sell them after there done cause I wanted to do something else. But thats where Im at in my life, Im in my 40's, semi-retired, with some good investments that enables me with the funds and the time to do them in.

Without these things I wouldnt be able to enjoy it, all Im hoping for you is for you to be successful with your project and enjoy and learn from it. I dont know the status of your life now but you stated that you didnt car if it took 10 years to complete it. Alot can happen in 10 years. I know if it was going to take me 10 years to complete something like this- I personally wouldnt do it....

Since you mentioned you have seen some of my ventures on this Lambo project you may have seen that I was working on a twin turbo longitudual reverse rotation LS3 drivetrain for my Diablo before I did the LS4. This is a prime example, a way over complicated project that was going to be way too expensive and take too long to complete. I had this thought in my head of it being "cool" and different, ect.... One day I just thought WTF am I doing? Im trying to build something thats unproven, meaning Im not even sure its going to work well enough to drive down the road. And Im going to spend alot of money and time on this when it might be a total failure??? I then realized that I need to go to a professional that will help me design it or tell me it what it really was- a stupid idea...

Four months later I got a great running LS4 swapped in with paddleshifters that I can drive anywhere and I can upgrade the drivetrain should I feel the need. Four months ago I didnt know anything about building a EFI wiring harness from scratch or anything about putting together a complete tune for Microsquirt. So Im also always learning something also, but I have learned when a project is too complicated and should require to consult with someone who knows what their doing.

What happens if you get someone on some forum telling you "oh yeah you can do that, just do this and that, weld this to this, and put that there and you will be fine? Now the guy that told you this is a 15 year old high school dropout (example) that has never chanded the oil on his mommas Yugo.

Keep doing what your doing- research, research, research, but Im hoping you wont go out and drop a bunch of money on a cheap crappy replica kit and a drivetrain without consulting some sort of professional that can give you a solid plan.

Personally I havnt seen any awd replica setups, and there maybe a reason for that. Infact most performance awd cars/trucks I have encountered (with the exception of the Gallardo) have removed the front differential. Alot of real Diablos and older Mercy's owners will remove the front diff.

I have about 6 or 7 different front differentials out of different cars/trucks in my garage from when I was trying to come up with the reverse rotation LS3. They all seem to have some kind of drawback or weakness to them. Granted I havnt seen a finished LP640 replica on a custom chassis but I have seen some build pics and I cant see where or how you could fit a awd drivetrain in one.

Not sure if you seen these images before or not:
LS1 Rear Mid-Engine AWD (C5 Corvette donor)-64151_507649449282627_244221424_n.jpg

LS1 Rear Mid-Engine AWD (C5 Corvette donor)-532828_507902642590641_1516619612_n.jpg

LS1 Rear Mid-Engine AWD (C5 Corvette donor)-430252_507902629257309_1417847102_n.jpg

LS1 Rear Mid-Engine AWD (C5 Corvette donor)-67926_507902602590645_380488269_n.jpg

This is a custom built V-drive for a reverse rotation LS1,2,3,6,7,9 with a 5 speed install and it kinda shows how little room there is in there. If I was going to do another replica build I would would really consider this method.
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Old 05-11-2013, 12:12 AM
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You are a cool guy tonypaul. Thank you so much for taking the time to give me some good advice. You definitely have a lot more experience than I do. I really do appreciate you sharing.

I like to learn new things too. That is part of what motivates me to do the things I do. I also have a tendency to try to do things "perfect" which can get me into trouble. I may very well get in over my head on this but if I do, I'll just take a deep breath, back out a bit and re-adjust my requirements. I can always sell any engine/tranny I purchased that I no longer need. It really isn't that big a risk unless I panic.

BTW, my brother isn't just a mechanic although he is that. He is amazingly talented and a true professional. He has done a lot of custom fabrication work on 4x4s that have to stand up to insane abuse. We have swapped transaxles on other cars and just a couple of weeks ago, we were swapping a tranny. He is the ONLY reason I can realistically even hope to pull this off. Without him, this project would be too difficult and/or too expensive.

Your LS4 swap was inspirational for me. I had already seen that before you responded to this thread. I very well may end up going down this road. I am not dead set on ANYTHING. All options are on the table.

I know some people don't like AWD (and maybe I wouldn't end up liking it either). I like the idea of it but we'll see.

I would be very interested to hear about the drawbacks/weaknesses of the differentials you know about. What should I look out for?

I had *NOT* seen that particular V-drive install you posted images of. That is pretty sweet. Thank you for sharing. I will consider that as an option. It is also a good illustration that there isn't a lot of room down the center of the vehicle. That definitely needs to be considered.

So back to the original question - can this be done? As opposed to do you recommend I do it.

Can I take an AWD setup from a front mounted engine and flip it around to be a rear mid-engine set-up? Do you know one way or another? People do this with 2WD all the time. Have you ever seen it done with AWD by anyone? I think it would actually work. Like I said in my original post, the t-case power distribution would be a problem. The NV136 t-case used in the Astro for instance has a default 35/65 front to rear power split until it senses slipping. That means most of the time, I would basically be running in FWD unless I dealt with that somehow. But how? Is there even a way? This may be the show-stopper right here.

If you don't mind, I would like to bounce other ideas off you down the road as I get further into this project.

Mike

Last edited by BigPines; 05-11-2013 at 12:20 AM.
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Old 05-11-2013, 10:35 AM
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It would really depend on what drivetrain you are going to using. And when you say " flip' are you meaning front to back or upside down?

Most gears in front differentials are "reverse cut", if you was to either flip around or upside down the gears would be running backwards. Even if you were to flip it and rotate it so the gears would be going in the right direction you would be what they call "running on the back side of the gear". Which is not good, most gears are not ment to run backwards.

Most front diffs are also side specific, meaning shorter on the driver side or passenger side depending on the make. So alot to think about...

What drivetrain are you considering?
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Old 05-11-2013, 11:47 AM
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I'd like to just stick with the C5 drivetrain if at all possible since that is what I have. So, an LS1 engine and 4L60-E tranny. For now, I am considering running the tranny through the center of the vehicle between the seats (as shown in the above pictures you posted of the v-drive) and mounting an NV136 (Astro), BorgWarner 1372 (Syclone) or 4472 (Typhoon) t-case to it.

When I said flip, I was actually talking about flipping the engine/tranny front to back but obviously, I would need to do something in the differentials to compensate. I get what you are saying about it not being desirable to run a diff on the back side of the gears. I understand that is the reason you were trying the reverse rotation LS1. So other than doing that, what do people do to compensate? I could just grab the diffs from the Astro, Cyclone or Typhoon but they are not independent suspension. I'll need diffs anyway since I don't think I'll be able to use the rear from the C5 because I think it bolts directly to the tranny. Maybe I could modify the C5 diff so I could use it? So another great question, what diffs to get? Maybe a rear from an older Corvette (C4). Whatever I do, the gearing will have to match rear and front.

Maybe I am naive but as far as diffs being side specific, can't I just swap the axles and CV joints to make the pumpkin sit on whatever side I want? I could always do custom axles but that would add a lot of expense. I may have to do that anyway depending on the spline count of the axles I end up using and the Corvette spindles. I haven't got that far yet.

I still see the biggest problem with this idea is the power split of the t-case - unless I want a FWD Murcielago, which I don't think I do. Maybe the t-case can be modified/custom built for my application?

Where did those pics of the v-drive set-up come from anyway? Can I get more information on what they did on that build? It looks very similar to what I am talking about doing just minus the front drive shaft/differential.

Thanks again for the advice.

Mike

Last edited by BigPines; 05-11-2013 at 02:27 PM.
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Old 05-11-2013, 01:50 PM
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First I would figure out what gear ratio your going to need and thats going to depend on your powerband and size of tires. Alot of awd/front diffs come from trucks, suv's, and sport cars where the ratios are pretty low like 4.xx and may not be ideal with your size tires.

Depending on which diff you used you should be able to(in theory) to filp it and/or rotate it but you just dont know how its going to work untill you get in your hands . This is why I have 6 different front diffs in my garage cause its a process unless you consult with someone who specializes in designing something like this.

I keep having flashbacks when I was doing the reverse rotation LS3, and its just not something that can really be figured out completly without a some sort of chassis and maybe a body to see how its gong to fit. You might be able to figure out the concept/idea of it but if your set on trying this on your own your just going to have to invest some money on getting some diffs and suspension parts and going from there.

I just dont see how your going to get a awd out of C5 drivetrain without some kind of transfer case. And I cant see how a transfer case is going to fit unless you build some kind of custom v-drive with another output shaft.

I will have to search and find out where I found those pics of the v-drive, I just had them on my harddrive. But if I remember that custom v-drive was like $4k or something crazy like that.

If you cold get some kind of transfer case with a 1to1 ratio that was small enough you might be able use something like the front suspension off a awd astro van. But you would need a v-drive/transfer case that with a output of clock wise and another out on the other side that was counterclock wise. All in theory.....

I guess you really need to figure out of you want "something" awd or a replica. Building both seems almost impossible without some serious money.
Again "personaly" I just dont see it worth doing, 'IF' (really big if) you could get the rotation correct, and decent gear ratios, the custom c/v axles/hub/adapters/ect would put the project in major investment mode. Not even taking in considering all the additional metal bracing that would need to done. Your maybe adding an extra 400-600 pounds of dead weight thats going to effect the cars handling. And your going to have so many weak links in the joints your not going to be able put enough power to it to enjoy the awd. Plus you havnt even begain to consider the electronic management of drivetrain on the engine or trans side just getting all of that working/shifting with the ecu/pcm/controller/ect is going to be a nightmare within itself. But again thats just my opinion.

You can figure around $50k (if you budjet correctly) to build a decent 640 replica with your C5 drivetrain with either a reverse vdrive or a porsche transmission. Now if you did like you said just forget about the replica thing, (which you just cant do if your going to build a custom chassis for a awd replica) you set out to build only the drivetrain on the floor. Like you said just forget about the replica part, you might be able to mock it up to see if it might fit without such a major investment. You wont be able to set pinion angle levels and suspension travel but you would get a better idea.

Another suggestion would be to get something like this:http://cgi.ebay.com/ebaymotors/2001-...orcev4exp=true

That was a great deal, some pretty good deals pop up on ebay every once and a while. If you got something like that (ata good price) you could still try to mock up the awd concept and see if it wold fit. If not just swap in your LS1 with a vdrive or just finish what someone else started... Just an idea~
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Old 05-12-2013, 10:57 PM
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I kind of laugh when people warn that a nice build may cost $80K. I have heard this number thrown around a lot like it should be a shock or something. Maybe people haven't noticed but $80K for a nice car these days is not a completely insane amount. I accept that my build will eventually cost $80K (interest free I might add). I can handle that and continue to be undeterred. Let's get back to talking facts about this concept! I'm trying to figure out if I can make it work. If not, I will probably do the V-Drive RWD.

The stock C5 came with various gear ratios (2.73, 3.15 or the performance 3.42). Anything in that realm would probably be fine. If I am able to use my C5 diff, I just need a matching front. If I need to use a C4 diff, I'll get one to match that. So I'll probably try to get the same diff front and back and flip the front one or rotate it if necessary. That sounds like the "easy" part.

I may try to use an Astro front diff. It came in both 2.73 & 3.42 so it would probably work perfect. However, as I said above, I may not need to if I can simply flip / rotate a Corvette diff. If I stick with Corvette parts, I don't think I will have to worry about spline counts matching up. Either way, I plan to use the C5 suspension.

Our plan is to get the powertrain, body, suspension and wheels together to see how it would all integrate into a chassis. Adjustments will be made based on fitment. I think we can figure it out for relatively little money.

As I have been saying all along, I am planning to get a transfer case. I mentioned three specific AWD (not 4WD) t-cases above that should bolt up to my transmission. The NV136 is a viscous-coupled transfer case that will automatically transfer torque where it's needed with no additional electronics whatsoever (a similar concept is used in the Murcielago BTW). The NVG-149 / NP149 t-case is a heavier duty viscous-coupled option. Where are all the complicated electronics needing to interface with the engine computer? From what I understand, the newer AWD t-cases in these vehicles have an encoder motor in them to calculate when to engage/disengage. I would probably need an appropriate transfer case control module and possibly a vehicle speed sensor if I went that route so I will probably avoid that. If I am under-estimating the complexity of this due to my own ignorance please school me. What exactly am I overlooking that I will need? Does the transmission have to change the shift points just because I am going to AWD? I figured the only time that would come into play is low range which I won't have in an AWD t-case.

I can fit the t-case in the car - no problem. I will either steal a little passenger leg room for it or move it closer to the front diff so it won't matter. I really see this as a minor problem and not one I am concerned about right now.

So why is AWD sooooo expensive and heavy? What are the extra things we are talking about here? A front diff that matches the rear's gear ratio, front axles and a front drive shaft? I think that is it. If anything, this would probably actually help to balance the car out. That is a major investment? I need the transfer case either way or a V-Drive setup to take it's place which would almost certainly be as heavy and more expensive. I just don't get all the caution. I mean, if I do AWD and I really hate it, all I have to do is pull the front diff, axles and drive shaft out, sell them and presto - I have a killer 2WD set-up! Well, truthfully, the t-case would probably have to be modded/replaced because running 100% power to the rear all the time may damage it. Please tell me if I am being naive.

As for weak links in the joints and all the computer interfacing...you realize there are already several performance LS1 AWD swaps around right? How the heck did they pull them off? I'm sure I could find out from them. The only thing I am talking about doing differently is a rear mid-engine. That doesn't change any of the basic LS1 AWD principals as far as I can tell and rear mid-engine has already been done in 2WD.

http://www.theturboforums.com/thread...sembly-pics%29


https://ls1tech.com/forums/conversio...onversion.html


Any chance I could bring you to the dark side and talk you into doing a similar build?

Thanks tonypaul, you have challenged me to look deeper into this concept and I think it is sounding better all the time. I do know more now than I did when I first posted. However, I keep coming back to the same problem - the rear-bias power split in the t-cases mentioned above (which of course would become front-bias after the drivetrain flip). That really should be worked out to do this right and it may be too difficult or expensive to do. I think the power split is controlled by a planetary gear set in the t-case so I would probably have to get a custom gear set to change that power split. Does anybody do that? I don't know. The NVG-149 / NP149 t-case has a default 38/62 front/rear power split. At nearly 40/60, it is a bit better than the other options I have seen. Probably the biggest problem with just leaving the power split stock is having most of the power up front where there is less weight but at a near 60/40 front/rear power split after the drivetrain flip, it may not be THAT big of a deal. If it does slip, the AWD will adjust the power split accordingly. I may still have problems with torque steering though. Maybe I could intentionally change my diff gearing to alter the power split but that may also cause damage to the t-case if it reads that as wheel slippage and tries to lock up all the time.


That was a good deal on eBay. I wouldn't rule out doing something like that but eventually, I think I'm going to want to build my own and do it my way.

I am beginning to think you are correct about this forum not being the right place to ask this question. I have seen a ton of other detailed conversations regarding similar complicated matters on this forum by some very knowledgeable people. One of those threads is listed above. Unfortunately, other than you, I basically only hear crickets in here. What gives? Doesn't anyone want to build anything fun and cool anymore? Doesn't anyone know how? I don't. That is why I am here to learn. If I have to, my brother and I can figure this out on our own but it sure would be nice to get some good information before I waste the time and money with trial and error. In the end, I'll do whatever I have to do - even if it means going RWD.

Mike

Last edited by BigPines; 05-13-2013 at 01:02 PM.
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Old 05-15-2013, 12:52 AM
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Yeah I really didnt think this is the place to get the info you need. While there 'shops' out there that can do this type of projects they are more than likely not share their trade secrets to everyone.

Not a chance in hell I would take on a project like this. About 8 years ago I build a custom reverse rotation sbc/th425 street-strip thing in the back of a Fiero. Although it worked it had design problems. And after this recent reverse rotation LS3 thing.... No way, I m done building one off, totally custom stuff.
LS1 Rear Mid-Engine AWD (C5 Corvette donor)-backrear2.jpg

LS1 Rear Mid-Engine AWD (C5 Corvette donor)-sideback2.jpg

LS1 Rear Mid-Engine AWD (C5 Corvette donor)-pb030366.jpg

Some of which you might need to take in consideration when building your project. First is the oil pan/flow, your gonna need to go with a dry sump system if the engine is reversed. On moderate take offs the oil will flow up and out of the pan towards the front of the motor.

Second- I may be wrong on this, its been a while since I had a Corvette diff around here. With the diff being limited slip it will not function correctly running backwards. Not sure on what engine/trans mangement you will be using and if your going to be using speed senors or not but there is some areas in there you might need to look at as well. Plus you will need to plug the top vent and drill a new vent on what will be the new top side.

Third the handling is going to really strange. The torque steer is going to be crazy bad with the majority of the weight in the mid to rear of the car. It might be fine in a straight line, but powering thru a curve could get a little hairy. Your going to have to 4 corner scale the car for the proper spring rates. The factory C5 springs wont be even close for the proper transfer.

So bad news is I just gave you a bunch more suggestions to research....
Good luck! Let me know wen you make some progress on it!
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Old 05-15-2013, 10:55 AM
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That is a pretty neat Fiero. Could that thing actually get it's front tires off the ground? You probably don't have any video of it racing?

Yeah, my brother said right away we would have to do dry sump. It solves several problems including clearance for the rear drive shaft under the engine and we plan to move the oil cooler to the LP640 vent originally designed for this.

As for the C5 diff and running backwards...The design we seem to be going towards right now is a V-Drive between the tranny and t-case. These look pretty sweet: http://www.casalev-drive.com/ This will solve the front bias problem. It will give the t-case the correct orientation with mechanical coupling to the rear and viscous coupling to the front, plus I will get a 35/65 front/rear power split the way the AWD system was designed. The biggest problem is finding room of all that stuff. I think we will probably push it forward near the front diff. I may not have much front trunk storage by the time we are done cramming all that stuff in there but I think it will be worth it.

So, if the above happens, I won't need to worry about running the rear diff backwards. Either way, the C5 rear diff may be too large so we are prepared to go with Ford 8.8s if we have to. In the front we will need a reverse rotation diff anyway to avoid the gears running on the coast side. Luckily, my brother said the Ford 8.8 comes in reverse rotation (in the front diff of the Explorer for instance) so we are tentatively planning to snag one of those.

You could be right but I really don't think the handling is going to be that bad. The majority of the torque will be in the rear axles and we will have more weight up front than the average build due to the AWD components. I realize torque steer still may be an issue but there are a number of things we can do to mitigate that and we'll just have to deal with it if we make it that far. Again, if the thing is a death trap and we can't fix the torque steer, I'll just yank the FWD.

This is going to be a long term project but I will definitely share whatever we end up doing. Either way, it will be a blast!

Mike

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Old 05-16-2013, 12:26 AM
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A few things to consider:

The two axis's of a v input and output shaft are divergent. Hence the name V drive. the included angle would have to be very near 0 degrees for best angularity. An ideal setup would be like a V drive but with the axis's of the drive gear and driven gear being parallel and having the proper output rotation.

The corvette transmission is not a good candidate, your way better off with an F-body or other conventional engine mated directly to transmission setup.

Next, on to the diff. The GTO diff may swap into the cradle of the C5 to allow a drive line to be attached. The housings are drastically different but you would probably have an easier time getting the cv axles working and this would allow an easier connection to the drive line. Your input will still be near the centerline of the car so your balancer will want to be in the same place as your yoke or flange on the pinion unless your engine is obscenely high.

If you look at the Lambo setup there is a bespoke gearbox that keeps the rear axle centerline very close to the engine and has a centrally located output for the forward diff. That is the ideal situation.


I see the vast majority of your budget going to fix drive problems. Rear drive would be a piece of cake.
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Old 05-16-2013, 02:19 AM
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Thanks for your input markbsae. I think I understand what you are saying about the V-Drive angle but I don't understand why it is a problem. I believe the attached image of the casale v-drive illustrates the angle. I believe it is actually 12 degrees. However, if u-joints or CVs are used at the connections, wouldn't that eliminate the angle issue?

Why exactly is the 4L60-E not a good candidate?

So you are saying a GTO diff is better than a Ford 8.8 diff for some reason?

In theory, the engine will end up just above the rear diff so there will be just enough clearance for the rear driveshaft. This assumes the use of dry sump and the associated much smaller oil pan.

Maybe you don't understand what I am proposing. Let me try to explain again. The LS1 engine will be mounted in reverse to the inside of the rear axle and up against the firewall in the rear. The tranny will either be mounted directly to the LS1 (by removing the torque tube and changing out the input shaft) or the torque tube will be shortened. The output shaft of the tranny will run to the V-Drive which will be near the front diff. The t-case will be connected to the other shaft of the V-Drive. The rear drive shaft will run from the rear side of the t-case under the transmission and engine to the rear diff. The front diff will be connected to the front side of the t-case (possibly via a very short drive shaft).

It will cost some money to deal with a t-case, v-drive, front diff & custom drive shafts. So like $3K extra for the AWD parts. That doesn't sound too bad to me. Am I missing something?
Attached Thumbnails LS1 Rear Mid-Engine AWD (C5 Corvette donor)-img_0381_0001_cp-4.jpg  

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Old 05-16-2013, 08:28 AM
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Just a thought to throw out there, I know with the old 4.3l you could get cam and everything to run reverse rotation through the marine suppliers for boats....I wonder if they have kits for the ls series motors now, but the oiling system might get expensive...that way you could almost take an awd setup out of a production car/sub built now and put everything in backwards so the engine is in the rear. Anorher option would be to run a divorced transfer case off of a gear to gear reverser (not sure of the exact name) off the back of your tranny.
I've also seen people use adapter plates to bolt just about any engine to any tranny, so you could even run a different transaxle out of a rear/mid engine vehicle to an ls motor.


Yes all of these options found easy on paper, but with some work and money can be done
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Old 05-16-2013, 10:57 AM
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Thanks mark21742.

Yes, a reverse rotation LS1 can be done but I don't want to mess with that. I think that would only cause more complications/problems and add expense. Do automatic trannys like being run in reverse rotation of their design? Nope. What about t-cases? Then I still have the t-case power split front-bias problem to solve anyway. Nah...

I think your second suggestion sounds like our tentative plan. We need to flip that t-case around to solve all the big problems. This will probably be done using the V-Drive. We basically just need to figure the specifics of the connections and if we can make everything fit.

Last edited by BigPines; 05-16-2013 at 11:55 AM.
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Old 05-16-2013, 01:44 PM
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Where is the front of your engine in relation to your rear diff? What front diff are you thinking of trying to use?
In your above description I cant figure out how your placing everything and it seems like you got one rotation going the wrong way.
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