17 hours ago in Articles
Tips from a Skip Barber Racing instructor.
I have a project kicking around in my head and it involves using a longitudinal mid-engine setup like you'd see in a GT40 replica or the Factory 5 GTM.
I plan on using a GM LS based V8 (L33 5.3 is at the top of my wishlist currently). With a few bolt ons, that engine is capable of 400 reliable horsepower.
My question to the vast knowledge of the GRM collective is: Which transaxle should I use? Horsepower/torque capability, overall length, and shifter type/layout are the main criteria. The weight of the vehicle in my head will be about 2200lbs.
Since I want to keep this as grassroots as possible, I don't want to hear about ZFs from Panteras, Hewland FT/LD200s, or any other hyper exotic transaxles (unless you have one taking up space that you would give away ).
Here's a short list of what I have dug up so far:
VW/Audi 016, 01E, 01M. Pros: Kennedy already makes adapters and there is a company that makes cable shifters for most of them. Relatively inexpensive and plentiful. Cons: Questionable durability depending on who you ask. Some of the GT40 guys break them at track days (I don't know at what horsepower level though).
Porsche 915, 930, G50. 915 is not known for its durability, but the side shift 915 out of a 914 might be interesting. 930 is only a 4 speed, but it is the shortest from bell housing to tail. The early ones also have the shortest distance from the face of the bell housing to the center line of the drive axle output flanges. I know very little about the G50. Factory 5 does recommend it for the GTM. Although it can be done, these transaxles are kind of expensive to convert to side shift. These transaxles aren't exactly cheap period.
What say you wise ones?
Might be pricey, but what about a corvette transaxle. Seems like a good match for an Lsx. 944 version of the 016?
The 914's transaxle (called the 901) is not really stout enough for a V8. If it breaks, it's $$$ to fix, too. Gene Berg Enterprises http://www.geneberg.com/index.php has a lot of update stuff for the old VW Bug transaxles but again $$$.
The Corvette transaxle is probably the strongest and most readily available. But due to the rearward diff placement it's going to move the engine further forward in the car. So that pretty much leaves you with the Porsche transaxle.
Or you could cobble up something of your own. The Olds Toronado/Cadillac Eldorado transaxle had a diff which bolted to the side, so to speak, and used a chain to transfer power from the automatic gearbox. So theoretically it's possible to use a T56 or similar, make a custom extension housing and output shaft, then adapt the chain drive setup to spin the diff.
I think the Audi setup is probably the winner.
How about a Subaru tranny with the rear output locked? I've seen (on the internet) where that setup has been used in MR configurations. There is a Piorsche speedter and/or 550 Spyder replica builder in TN that does it that way. There is also a company in Oz that sells the parts needed for the conversion - I think they do it for dune buggy/sand rail type applications.
oldtin wrote: Might be pricey, but what about a corvette transaxle. Seems like a good match for an Lsx. 944 version of the 016?
The Corvette transaxle has the diff at the wrong end. It's basically a Tremec with a Getrag diff bolted to the output shaft. I need the diff as close to the bellhousing as possible.
The shifter on the 944 016 goes through the bell housing into the torque tube. It's actually easier to use the 016 from a FWD Audi 5000 turbo.
Here's a link to the site where I found all the cable shifter setups:
Curmudgeon wrote: The 914's transaxle (called the 901) is not really stout enough for a V8. If it breaks, it's $$$ to fix, too. Gene Berg Enterprises http://www.geneberg.com/index.php has a lot of update stuff for the old VW Bug transaxles but again $$$.
I knew the 901s were not strong enough. For some reason I thought the later 914s used a 915. I could be wrong. It's been years since I was under the back of one of those.
I've seen the Gene Berg stuff. I agree that it's a little pricey.
Curmudgeon wrote: The Corvette transaxle is probably the strongest and most readily available. But due to the rearward diff placement it's going to move the engine further forward in the car. So that pretty much leaves you with the Porsche transaxle.
Exactly. That layout just won't work.
Curmudgeon wrote: Or you could cobble up something of your own. The Olds Toronado/Cadillac Eldorado transaxle had a diff which bolted to the side, so to speak, and used a chain to transfer power from the automatic gearbox. So theoretically it's possible to use a T56 or similar, make a custom extension housing and output shaft, then adapt the chain drive setup to spin the diff.
Interesting idea. A little Rube Goldberg. I don't want to get to far from just having to have custom axles, shifter, and adapter though.
Does anyone know what the Boxter and Caymens have used throughout their lives? The Boxster's been around long enough that parts should be more readily available from the salvage yards. I don't know why i didn't think of the Boxster when I made my first post.
Keep the ideas coming. I can't think of a better forum to brainstorm this kind of idea on.
IIRC the Boxsters used 01E (Audi) transaxles. Could be wrong.
The FWD 016 is not super easy to find and not really strong enough for a V8. The AWD 016 is stronger but still probably will break with the torque. They cope with turbo fives well enough because the power tends to be softer, if that makes sense. Even then, when they get up around the 500-600hp mark, they start to get iffy.
On the other hand, it's probably the best of all options.
The folks building Factory Five GTMs like to talk about this...
theenico wrote: <I knew the 901s were not strong enough. For some reason I thought the later 914s used a 915. I could be wrong. It's been years since I was under the back of one of those.
Early 901s used a rear linkage that went all the way around the engine and transmission to the very back of the car. made for very slopping shifting.
Later 901s had a "side shifter" that was better
The short lived Porsche 916 used a turned around 915 transaxle.. called.. wait for it.. the 916.
You can flip a porsche trans around.. you can also flip it upside down to lower the engine even closer to the ground.
Giant Purple Snorklewacker wrote: Boxster Transaxle on ebay... 82k
Yeah, that just screams Audi 01E. Even the bolt pattern looks the same from this angle, right down to the crank sensor notch and TDC hole used on the five-cylinder engines.
VWAG/Porsche: We re-use everything!
Of course, now I am thinking TDI engined Boxster, just to piss off all sorts of different kinds of purists.
I completely skipped over the Boxster unit. In a lower HP application (maybe up to around 300 or so), that might be the shizznit; Porsche has already done all the hard shift mechanism engineering.
I think the trick is the torque - the Boxster / Cayman cars were in the mid 220 to 280 ft lbs and that is barely going to tolerate soft pedaling an LS motor unless they are grossly over-built. Since this seems to be an Audi part - what is behind the S4 V8? A better one of these?
Will the trans from a 951 work. Open dif versions are relitivly cheep. I think they can Handel the HP and torque you are looking at.
I think the shifter will be a problem with the 944 etc transaxle since it goes through the bellhousing right where the flywheel clutch etc need to reside. Not insurmountable, though.
Acura Legend V6 had a longitudinal layout and both 5 and 6 speed gearboxes available.
chaparral wrote: Acura Legend V6 had a longitudinal layout and both 5 and 6 speed gearboxes available.
I'd heard they only came in auto, or maybe that's all anyone found in the junkyards.
A really good place to look for info on this subject is the Powertrain section on GT40s.com's tech forum.
carguy123 wrote:chaparral wrote: Acura Legend V6 had a longitudinal layout and both 5 and 6 speed gearboxes available.
I'd heard they only came in auto, or maybe that's all anyone found in the junkyards.
V6/6sp models are very rare but they do exist.
GRM Story: My boss's brother bought a mint black V6/auto Legend for relative pocket change, then borrowed the shop one weekend to do a 6-speed conversion. (He lived ~150mi away at the time) Manual transmission conversion on a Legend apparently involves fabrication since the firewall is different and things like the pedal box aren't a direct fit. Something about a spacer needed to be fabricated, I don't know the details. Anyway it was a solid weekend's work, but he did drive it home late Sunday night. And at the end of it all, he had a "unicorn" black V6/6sp Legend, which if he ever found one for sale would have run him about double what he had into this one.
Anyway, point of all this: The Legend transaxle is similar to the TH425 imaged above. The transmission sits behind the engine, and the differential plugs into it and bolts to the side of the engine. Not sure if it's quasi-integrated with the oil pan or not.
And a quick FYI on the TH425. The chain drive does not transmit power from the trans to the diff. The chain drive transmits power from the torque converter to the transmission's gearset. BIG difference! The transmission is basically a TH400 that was folded in half at the front pump, with a heavy cast-iron differential stuck on the end.
There's the legend setup, that's actually the auto but it shows the diff hanging off the front.
Per previous thread:
I've spent a fair amount of time on that GT40 site. Lots of good info, but they are fairly inconclusive about transaxles. Of course, if money were no object, this would be easy. I'd just buy a PBS, Weddles, or Albins like the super rich sand car guys that run 1100hp LS engines.
It seems like I always keep coming back to either the Audi 01E or Porsche G50.
Here's a link to a fairly high horse car using the 01E:
Does anyone know anything about the BMW X5 or 535Xi or 325Xi transaxles? In older BMWs they used mostly the same part in everything so it was overbuilt to handle the top of the range. They come with a stout V8 or a torquey turbo and have manual trans configurations as well. The junkyards must have a few of these handy.
I've rolled the idea of a typical mid-engine V8 car around for about 30 years. Never did it because I kept coming back to only one solution, a proper but expensive Porsche transaxle. Because of the very high cost I ended up just building lighter cars and using an entire FWD assembly. You might look into using the entire FWD package from something like the Cadillac SVCC-SCI... or whatever they call that 500hp version... Yeah I know the engine's sideways, but either you have to compromise, or pony up the money to do it the way you want.
1 week ago in News
We're on our way to the Classic 12 Hour at Sebring.
Also get your instant access to the digital edition of Grassroots Motorsports Magazine!Learn More