Can't figure out steering rack solution on odd swap...
10-11-2011, 12:02 AM
#1
Staging Lane
Thread Starter
Can't figure out steering rack solution on odd swap... Would love a creative solution to this. I'm planning out a LSx swap into a 2005 Subaru Legacy GT, using stock Subaru transmission, which needs to stay in relatively the same place as stock since it will stay an AWD car (otherwise there is no point).
Suspension is lower control arm with coilover attached directly to hub. Steering tie rod attaches to front of hub.
Stock steering rack sits at top of stock crossmember. Stock steering rack center is directly below the trans torque converter housing, with less than an inch clearance between steering rack and trans bellhousing.
Note: The stock engine and transmission rotating center are oddly high compared to the F-body and Vette, yet the engine is boxer (flat) so the hood is not very tall.
To make the swap work, I must lower the engine and trans to "normal" height.
This means lowering the transmission as much as 4".
Problem: Steering rack would need to move 4" down, or 4" forward if I use a GTO oil pan (I like this GTO pan option best). Either situation would ruin the car's great handling by messing up suspension geometry.
How do people solve this kind of problem???
My only idea is to weld a bracket on each end of the steering rack, which would move the inner tie rod ball joint to it's original location, but still have the rack out of the way and able to fit. A reaching bracket on each side. I am told by one engineer that no matter how perfectly I fabricate the brackets, it will flex and make the steering feel lousy. I've devised all sorts of stabilizing guides and things to keep the steering rack ends sliding in and out without flexing, but I am not a trained engineer or an expert at suspension or chassis fabrication, and as such don't have the expertise to do this right. Maintaining good suspension geometry is a must.
Any help would be much appreciated!!! TIA
Suspension is lower control arm with coilover attached directly to hub. Steering tie rod attaches to front of hub.
Stock steering rack sits at top of stock crossmember. Stock steering rack center is directly below the trans torque converter housing, with less than an inch clearance between steering rack and trans bellhousing.
Note: The stock engine and transmission rotating center are oddly high compared to the F-body and Vette, yet the engine is boxer (flat) so the hood is not very tall.
To make the swap work, I must lower the engine and trans to "normal" height.
This means lowering the transmission as much as 4".
Problem: Steering rack would need to move 4" down, or 4" forward if I use a GTO oil pan (I like this GTO pan option best). Either situation would ruin the car's great handling by messing up suspension geometry.
How do people solve this kind of problem???
My only idea is to weld a bracket on each end of the steering rack, which would move the inner tie rod ball joint to it's original location, but still have the rack out of the way and able to fit. A reaching bracket on each side. I am told by one engineer that no matter how perfectly I fabricate the brackets, it will flex and make the steering feel lousy. I've devised all sorts of stabilizing guides and things to keep the steering rack ends sliding in and out without flexing, but I am not a trained engineer or an expert at suspension or chassis fabrication, and as such don't have the expertise to do this right. Maintaining good suspension geometry is a must.
Any help would be much appreciated!!! TIA
10-11-2011, 12:11 AM
#2
On The Tree
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There is no way to fit a LS1 in a subaru platform while keeping the subaru AWD system. The engine would sit way too forward. Factory subaru engine is super short. LS1 is at least twice as long.
10-11-2011, 10:59 AM
#3
Staging Lane
Thread Starter
I've measured it in every which way and have another thread where there's a solution to the extra few inches of unnecessary accessory length, which was recently implemented on an LS1 swap into an Audi RS4. I am also friends with the guy who put the Buick 3.8 into his Legacy GT, and when I last visited him I specifically measured to confirm that it will fit.
Back on topic, anyone know anything or have experience with offsetting steering racks and working within constraints of suspension geometry?
Back on topic, anyone know anything or have experience with offsetting steering racks and working within constraints of suspension geometry?
10-11-2011, 11:21 AM
#4
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Is it not something that could be resolved with an AWD oil pan, maybe, like the Trailblazer SS? Ram the steering rack through it instead of the driveshafts. Dunno...without seeing it, I'm just hypothesizing wildly.
The problem with modifying steering on a daily driven car is that even the cheapest suspension and steering parts are normally some sort of engineered stamping or a forging. Making steering parts is sort of like making your own light switch for your house...possibly well thought out but your insurance won't care about the schematics when it fails and burns the place down. They work in race cars because they're constantly maintained and generally see fewer oddball loads than a street car.
OFF TOPIC FOR A MOMENT - Why not just boost the daylights out of the boxer engine? You got an LS1 burning a hole in your pocket?
In the porsche threads, those guys seem to be putting some heavy angles on their CV shafts. Maybe you could move the trans back a little bit and just deal with more CV angle?
There's an EVO on here that looks like the engine is on a serious tilt...I guess you could mess with that, too. Kind of take a half-and-half approach. Move back 2", move down 1".
Final thought...it sounds like it's a rear-steer setup. Can you make it a front steer, with nearly the same angles (mounting height, distance from hub center, etc.)? Like swap the spindles side to side or something. Again, I'm just throwing out stuff so you can shoot it down.
The problem with modifying steering on a daily driven car is that even the cheapest suspension and steering parts are normally some sort of engineered stamping or a forging. Making steering parts is sort of like making your own light switch for your house...possibly well thought out but your insurance won't care about the schematics when it fails and burns the place down. They work in race cars because they're constantly maintained and generally see fewer oddball loads than a street car.
OFF TOPIC FOR A MOMENT - Why not just boost the daylights out of the boxer engine? You got an LS1 burning a hole in your pocket?
In the porsche threads, those guys seem to be putting some heavy angles on their CV shafts. Maybe you could move the trans back a little bit and just deal with more CV angle?
There's an EVO on here that looks like the engine is on a serious tilt...I guess you could mess with that, too. Kind of take a half-and-half approach. Move back 2", move down 1".
Final thought...it sounds like it's a rear-steer setup. Can you make it a front steer, with nearly the same angles (mounting height, distance from hub center, etc.)? Like swap the spindles side to side or something. Again, I'm just throwing out stuff so you can shoot it down.
10-11-2011, 12:25 PM
#5
Staging Lane
Thread Starter
Thank you for being positive about this. I will do my due diligence on all the points you mentioned, though off the top of my head none will work alone (but you never know until you explore everything). Actually the serious offset of front half shaft axles will be necessary. I just don't want to overdue the angle unnecessarily, though I am very interested to see what the Porsche guys have done. It's basically the same swap, just on reverse ends 
The trouble with the 2.5L EJ25 is the driveability. The biggest turbo I can see getting away with and having the car completely streetable is a 44lb/min twinscroll 20G-ish, which would produce a very wide powerband and some grunt when the light turns green on the street. So on E85 and 24psi, call it 400whp or 530bhp, with a lot of torque to match. So to make it worth my while, the LSx would need at least 600bhp, which means turbo! So the idea is to completely solve all swap issues, then start working on the cheapest way to get it swapped properly, part by part. Then turbo the LS. So long story short, the LS is a solution to the Subaru trap of spending $10,000 on a damn engine, only to then spend more to re-turbo it so big that you get zero power below 4000rpm, ever, and **** reliability. I would rather it be safer and more drivable and effectively cheaper, by doing LSx with good heads and cam and turbo(s). The axles concern me, but we'll see. I'm actually excited the swap requires lowering the engine, as the center of gravity will be real nice!
The trouble with the 2.5L EJ25 is the driveability. The biggest turbo I can see getting away with and having the car completely streetable is a 44lb/min twinscroll 20G-ish, which would produce a very wide powerband and some grunt when the light turns green on the street. So on E85 and 24psi, call it 400whp or 530bhp, with a lot of torque to match. So to make it worth my while, the LSx would need at least 600bhp, which means turbo! So the idea is to completely solve all swap issues, then start working on the cheapest way to get it swapped properly, part by part. Then turbo the LS. So long story short, the LS is a solution to the Subaru trap of spending $10,000 on a damn engine, only to then spend more to re-turbo it so big that you get zero power below 4000rpm, ever, and **** reliability. I would rather it be safer and more drivable and effectively cheaper, by doing LSx with good heads and cam and turbo(s). The axles concern me, but we'll see. I'm actually excited the swap requires lowering the engine, as the center of gravity will be real nice!
Trending Topics
10-11-2011, 06:49 PM
#8
4in down will make for crazy bump steer, 4 in forward would be better but far from ideal. I understand the awd stuff but why a subi ? those and audis are the worst awd swaps engine placement just sucks.
bmw 3 or 5 series
infinity g35/g37 350/370z
gto, ctsv
These are cars I would look at if I had to do it again. All these cars were longitudinal engine and within the platform were available with some form of awd
bmw 3 or 5 series
infinity g35/g37 350/370z
gto, ctsv
These are cars I would look at if I had to do it again. All these cars were longitudinal engine and within the platform were available with some form of awd
10-11-2011, 10:25 PM
#10
Staging Lane
Thread Starter
Reason for LGT receiving the motor is I have the whole car and transmission setup the way I want it. Anything with the word "Porsche" in it sounds very expensive, and very customized, even more so than this swap. I'm not done with this idea yet, but starting to warm back up to the idea that the motor will continue to be Subaru for quite a while.
10-12-2011, 12:21 PM
#12
What about a awd trailblazer transmission. Or there is the guy that put the rack through the rear sump! There are always options, just might have to get creative.
But I am glad we decided to go rwd on our Subarus, lol. Just an engine cradle/subframe and we should be good.
But I am glad we decided to go rwd on our Subarus, lol. Just an engine cradle/subframe and we should be good.
10-12-2011, 05:56 PM
#13
Staging Lane
Thread Starter
Where is the thread for that? I can't find it.
Here is what it sort of looks like. Steering rack sits under the flex plate (stock). You can see the front diff directly under/behind the torque converter.
If I swap to the GTO oil pan and slide the whole assemply backwards a couple inches, there is a chance I can sneak the steering rack in place of the blue oil filter as pictured. As ridiculous as this looks, I've driven and closely looked over the 3.8L V6-swapped Legacy GT with engine dimensions that are VERY similar to the LSx swap that i have worked out, and believe it or not it's really not a bad setup.
Here is what it sort of looks like. Steering rack sits under the flex plate (stock). You can see the front diff directly under/behind the torque converter.
If I swap to the GTO oil pan and slide the whole assemply backwards a couple inches, there is a chance I can sneak the steering rack in place of the blue oil filter as pictured. As ridiculous as this looks, I've driven and closely looked over the 3.8L V6-swapped Legacy GT with engine dimensions that are VERY similar to the LSx swap that i have worked out, and believe it or not it's really not a bad setup.
10-12-2011, 09:32 PM
#15
Staging Lane
Thread Starter
Overdue replies:
It's already front steer.
Let me know if you find it. I have half a mind to take this as an opportunity to get a good grip on suspension geometry, and see about taking a ground-up look at the suspension (fingers crossed something will present itself).
It's not about AWD so much as lots of limited slip functionality, and being able to hold massive power. I have an awesome front TBD on the 5eat. The rear diff works fine for now, or else I'll upgrade it later (with a used, reasonably-priced aftermarket diff). The center 5eat diff is an amazing piece from the factory.
I don't know much about these other cars, but I suspect my current AWD system can handle a LOT of punishment, and I'm sure I cannot afford to make most of these other cars do the same (at the moment). I'm not switching platforms just because of a steering rack. No it's not rational.
However, you bring up a great point, that the G35x or G37x would be one hell of a platform IF there are solutions to make them hold the power. I don't know enough about them yet. Good idea
Porsche would be expensive and complicated. Swapping in a new AWD trans would be a mess, far more than this project already is. Cost would go through the roof. My stock trans is fine as is, very strong, already modified in all the right places, and I can make it do or tolerate whatever I want.
They look very sweet, but they don't solve the fitment problem.
It's already front steer.
4in down will make for crazy bump steer, 4 in forward would be better but far from ideal. I understand the awd stuff but why a subi ? those and audis are the worst awd swaps engine placement just sucks.
bmw 3 or 5 series
infinity g35/g37 350/370z
gto, ctsv
These are cars I would look at if I had to do it again. All these cars were longitudinal engine and within the platform were available with some form of awd
bmw 3 or 5 series
infinity g35/g37 350/370z
gto, ctsv
These are cars I would look at if I had to do it again. All these cars were longitudinal engine and within the platform were available with some form of awd
I don't know much about these other cars, but I suspect my current AWD system can handle a LOT of punishment, and I'm sure I cannot afford to make most of these other cars do the same (at the moment). I'm not switching platforms just because of a steering rack. No it's not rational.
However, you bring up a great point, that the G35x or G37x would be one hell of a platform IF there are solutions to make them hold the power. I don't know enough about them yet. Good idea
They look very sweet, but they don't solve the fitment problem.
10-16-2011, 05:24 PM
#16
Staging Lane
Thread Starter
Porsche CV angle FTW.
The buggy racing guys are using Porsche 930 and 944 CV joints and running 22-23 degrees without any concerning failure rate. More heat, more friction blah blah lots of things will need to be serviced more often on a 600whp Subaru, CV joints are a price to pay. I don't think I will need nearly that much CV angle either.
14 degrees if the half shafts are 24" with a 6" offset*.
18 degrees if the half shafts are 18" with a 6" offset*.
*I do not know the length of the half shafts from joing to joint yet. 6" is likely more offset than I will need.
This is still a lot of angle, and I will confirm tomorrow when I get under the car.
The buggy racing guys are using Porsche 930 and 944 CV joints and running 22-23 degrees without any concerning failure rate. More heat, more friction blah blah lots of things will need to be serviced more often on a 600whp Subaru, CV joints are a price to pay. I don't think I will need nearly that much CV angle either.
14 degrees if the half shafts are 24" with a 6" offset*.
18 degrees if the half shafts are 18" with a 6" offset*.
*I do not know the length of the half shafts from joing to joint yet. 6" is likely more offset than I will need.
This is still a lot of angle, and I will confirm tomorrow when I get under the car.
10-20-2011, 04:59 PM
#19
Found it! Not sure how applicable it is, but here was the suggestion.
I didnt read the whole thread, but I saw some talk about excessive bumpsteer due to moving the rack down. What I did when I put a rack in my 73 camaro was.. turn down and rethread the inner tierod. Then instead of using I stock style outer tierod you can use a spherical rod end. This allows you to use a small spacer to make up the difference between the tierod and the spindle or steering knuckle. You will also have to drill out the outer tierod stud hole in the spindle. Doing this I have kept the stock geometry and have no excessive bumpsteer.
