Ironfreak

I got a great deal on a low mileage transmission/engine package for my build. I've done a little research and want to accomplish a few things. I have heard that the truck transmissions aren't as strong as the f-bodies, can anyone confirm this? and why, somthing to do with the servos?

I also want full manual shifting. this is going into a 1988 bmw autox car. I have had a few guys say go with the transgo hd2 shift kit and get the Sonax 2-3 shift valve upgrade. Can you confirm this?

Last, its not a drag car, more autox, dd fun ride, what converter and stall speed do you guys suggest?

Engine-
LM7 - stock bottom end and cam
ls7 lifters
head studs/mls gaskets
60lbs. injectors
gt45 turbo

Expecting 500-550whp.

Thanks for your input in advance!

thunderstruck507

iTrader: (18)

Truck transmissions are almost the same minus the tailhousing (trucks don't have panhard bar mount) and the servo on the side (~$20 part). Most or all of them also use a deeper oil pan and longer filter which is a good thing.

Install the fbody/corvette servo, the HD2 kit, and the Sonnax valve for sure. It still may or may not live long behind that kind of power. Get a large trans cooler for sure as well.



Any reason you want the full manual shift option? The "stage 2" install of the Trans Go kit allows auto shifting in D and OD but still manual control as well.

Ironfreak

So get the corvette servo, check. Which transgo hd2 kit? I heard there is two different ones. Reason for manual shifting is I want to me able to lock in into gear. Most autox courses around here based on what I figured my speed range would be with this tranny and diff will be ran almost always in second and maybe bumped into third. I want to be able to control the shifting though. but also be able to drop it in OD when I'm rolling on the highway.

I was concerned that the trans might have a hard time with that power. But my car is stripped, I'm going for a finish weight of 2500lbs. when it's done. hopefully not having to push so much car will help a lot.

thunderstruck507

iTrader: (18)

EDIT: reading again, this kit listed below might not be what you want either...wait for a pro to advise, this kit may take the PCM out of the question and replaces with vacuum line equipment

This is the full manual kit, not the HD2 ( I thought the HD2 came with the parts to choose):
http://www.transgo.com/products.php?...dcountview=Yes

2nd gear with a 26" tall tire, 3.42 gear, and ~6500rpm rule of thumb lets me get to over 80mph
It would take a very fast autox course to need 3rd gear. IIRC the SCCA tries to keep MPH for the fastest cars under 60mph but I might be mistaken.

I have had mine on several autox courses and even a 1.2 private road course and the HD2 kit let me do everything I ever needed to do. I also drive it very spiritedly on curvy roads without issue. The only key being no stabbing the throttle hard mid turn if the trans is in 3rd and I'm running under ~74mph.

If it is a car you intend to enjoy on the street very often or take on cruises, I would go HD2. If it's a straight up autox duty car you might be happier with the manual kit.

Just my opinions and I will add I do not know if the same rules apply to turbo cars as NA. There might be other concerns with auto downshifts at high torque levels from a turbo engine.

thunderstruck507

iTrader: (18)

You do for sure want that 2-3 shift valve. I believe not having it was a large factor in why I have burned through the 3rd/4th gear clutches but the rest of them look like new.

Ironfreak

So with the HD2 kit can you still manually shift 1 and 2 gears? or when you autox do you pop it in drive and go? just curious. I will have just under 26" tires, and have the option of a 3.73lsd or 2.73lsd.

thunderstruck507

iTrader: (18)

the HD2 will hold 1 or 2

Example: Put shifter into 1 at start of course and get into 2 ASAP so you can focus on the course, the trans WILL NOT go back to 1st on its own. If need be you can manually downshift to 1st at any MPH (unless blocked by the PCM), but with any power this is usually slower as it causes wheel spin. This will be best as it will prevent unwanted or unexpected downshifts to 1st gear at WOT on a tight area of a course.

Example 2: if shifter is put in 2 from a dead stop it will leave in 2nd, not first

Example 3: shifter in D/3rd position, car will leave in 1st, auto shift to 2nd, auto shift to 3rd...will downshift all gears just like any normal car based on MPH and throttle position (this is the gear I drag race in and where the 2-3 shift valve comes into play as it leaves the extra over run clutches engaged so that 3rd gear has more holding power)


Hope this helps clear up how the HD2 kit functions. If not I will try to explain better or could even try to make a video.

Ironfreak

Awesome man, love the feedback, it's exactly what I needed to hear. What do you think for a stall speed? it shouldn't have to be extremely crazy would it?

This kit correct?
http://www.transgo.com/products.php?...dcountview=Yes

Servo kit?
http://www.calspeedperformance.com/p...p/trg-7-2p.htm

Sonnax shift valve?

thunderstruck507

iTrader: (18)

Yes all of those parts look correct to me. (Message the guy selling the 2-3 valve, he may be able to get you all the parts you are looking for and combine shipping, he is an outstanding vendor who went out of his way to help me get that part quickly after I accidentally had it shipped to the wrong address). He is also honest and will tell you if he can't get what you need for a decent price due to his supplier costs.

I do not know enough about turbo setups to recommend a stall speed. I try to be helpful where I can so people get quick answers but am definitely not an expert on all of it.

mrvedit

I'm glad that thunderstruck could give you such fast and accurate advice.
He is a graduate of the "School of Hard Knocks", which has a campus near you too.

The "Gear Command" option of the HD2 kit would do very close to what you want. IMO that option might not even be needed if you tune the trans for what you want. Also, the HD2 kit will give you very fast shifts if you simply leave in in [D3] (which is what you should use when the 2-3 shift valve is installed). I've made internal mods to my 4L65E too and shifts are incredibly fast. If I go from cruising to WOT, I'm pretty sure the trans has downshifted by the time the gas pedal hits the floor. Really! Maybe 50 ms? Even without the internal mods, I think the shifts can be under 100mS.

I don't install the HD2 "Gear Command" option so that the PCM can protect me from an accidental downshift which would exceed Redline.

mrvedit

For Auto-X I'm thinking a relatively tight 2400-2800 stall. Some members here do Auto-X and might have better advice.

Ironfreak

Thanks for all the feedback guys I appreciate your input. I just drove two hours last night to checkout this motor, steal of the century. 2002 LM7, 4L60E and brand new painless wiring harness for $700........did I mention the motor has under 50k miles! The heads are still all polished and shiny from the factory!

As I get into the tranny I'll bump this so keep an eye out as I might have some questions.

Thanks again!

mrvedit

That certainly is the Steal of the Century!
Good luck with it all.

thunderstruck507

iTrader: (18)

That might be what I am thinking of with the HD2 kit.

The way mine is installed, it will downshift on command from the shifter UNLESS the PCM tells it otherwise based on MPH. I left the MPH on the conservative side for 1st gear so that I don't accidentally over rev due to the severe gear jump between 1st and 2nd.

On an autox course this would be a situation where I am in a tight tight spot and think I am running too slow and lugging the engine in 2nd so I pull it back into 1st...often I find that I was "wrong" and the transmission won't actually drop to 1st until I shave some more speed at which time it will drop into 1st gear and stay there no matter what until I shift up again manually. I like this downshift fail safe but it can be removed or fine tuned in the PCM.

I never have this issue downshifting into 2nd from 3rd because those gears aren't split so far and it's easier to realize based on speed and audible engine speed when I can and can't downshift.

I want to say my 2nd gear goes to 84 or 85 mph commanded shift point before smacking the limiter during the shift. I only reached that MPH on the straight section of the road course I was on.

Ironfreak

I'd love to see video of your Chevelle racing the cones, that's got to be insane!

thunderstruck507

iTrader: (18)

Don't have any autox stuff I can find right now but here are a couple from the road course.

This video is the 2nd day I was invited, on MT ET streets rear and 235/60r15 street tires up front. You will see it was made more for a little mini indy type car so the lanes aren't overly wide and not really any run off...leads to us being very cautious.

First lap is power lap, second is cool down



this is my first time around the track aside from a slow "getting to know you lap" so it's pretty slow and boring to watch IMO but we were there for fun, street tires all around


and just for reference this is the track owner and I was riding along. Procharged 6 speed c5 on Gforce...most terrified/ happy I've ever been on 4 wheels, got out of his car shaking. We beat the time of an experienced sport bike rider who was on his race prep bike by a couple tenths

Ironfreak

where is this track?

thunderstruck507

iTrader: (18)

here in NW Arkansas, some construction tycoon built it to race little mini indy car /oversized gokart things on years ago before the economy took a dump

a friend bought it and has let us play around on it a few times, haven't been out there in over a year though...he began getting leery of legal responsibilities and/or getting noise complaints from nearby golf course patrons

he bought a surplus of go karts from a closed amusement park though and I think he recently began making some dirt mounds in the field for ATVs and dirt bikes to mess around

Ironfreak

Bummer, that looks like a lot of fun. I'm in Omaha, only about 5 hours from fayetteville arkansas. Our local track is closing.......won't get to even drive the finished product on it.

thunderstruck507

iTrader: (18)

There is a track outside Tulsa called Hallett. The Power Tour even swung through there the year before last.

Might look into that if there isn't a closer one