Learn me, corvette torque tube/transaxle

Specifically a c5 torque tube and transaxle set up.

1. Benefits and drawbacks of a setup like this?

2. Could you swap this to any ls type engine for a junkyard style swap? 
 

3. Is the transmission different from the normal 4l60e or t56? 
 

As you can see, it takes up a lot of room.  Deep servicing is also a royal pain.

The main advantages are that you gain a lot of lateral interior room, especially in the footwell area, because the torque tube is narrower than a transmission.  (I was introduced to Corvettes before the C5 existed.  Driving a C4 was like getting into a soapbox derby car, but from the side.  The C5 was a revelation)  You can also get the engine to sit a lot lower because the trans no longer hangs below it.  The oil filter is practically the lowest point of the car and the valve covers are at tire height.

In that image, for reference, the suspension is fully topped out against the bump stops.  The bottom of the catalytic converters is roughly where the floor is.

The transmissions share some internal parts but are very much Corvette specific.

At one time I had dreams of putting this under a "farm truck" to pick on sports cars at HPDE events. That thought progressed to thinking about putting it under a kit car shell and chassis to really mess with sports cars. Alas, the thought experiment ended after figuring the likely total expense.

Another advantage is that drivetrain torque is not transmitted through the chassis. 

Porsche transaxle cars are torque tube, as is the lowly Opel GT. Not sure what else but I will be building one.

Keith Tanner said:

Another advantage is that drivetrain torque is not transmitted through the chassis. 

It isn't?  

...No, I suppose it isn't.  The torque resolves through the torque tube, unlike a power plant frame that is necessarily fairly weak in torsion.

(And it is kind of weird to use the Mazda term for that... the earliest I know of that device is the last few years of C3 Corvette.  All C4s had one)

Take this with a grain of salt (confirm before you buy) but here is my understanding.

All T56 main housings (the center part of the case) are interchangeable.  All gearsets are interchangeable.  What differentiates them is the front plate, input shaft, output shaft, and output housing, in this situation, the differential.  An example:  I took a TNET1247-spec T56 from a Viper and converted it to GM with a GM front plate and input shaft and output housing.  I kept the beefy Viper output shaft and had the GM tailhousing bored out for the Viper bushing.  The center case has a little beefier ribbing as well as a viper emblem cast into it, but otherwise it takes the same gears, shafts, and bearings inside.

There have been many mid-engine swaps done this way by using a 'vette transaxle with the engine bolted directly to it.

As far as what parts are corvette-specific, I'm not sure, but it can be done.

Reach out to Rick at RKT Performance | Corvette and LS Performance Parts & Installation | Frederick, Maryland.  He has probably forgotten more about T56s than all of us put together.  As of about 8 years ago while he was rebuilding a T56 for me, he was shortening a torque tube to fit something else.

Pete. (l33t FS) said:

Keith Tanner said:

Another advantage is that drivetrain torque is not transmitted through the chassis. 

It isn't?  

...No, I suppose it isn't.  The torque resolves through the torque tube, unlike a power plant frame that is necessarily fairly weak in torsion.

(And it is kind of weird to use the Mazda term for that... the earliest I know of that device is the last few years of C3 Corvette.  All C4s had one)

4th gen F bodies had one too. 

So you've got the twist from the engine, but at the back you also have the rear end trying to torque its way upwards. The Miata PPF flexes in twist so it doesn't do anything to restrain the engine, but it does locate the rear diff and the transmission. That takes a big bending load out of the chassis. Since you don't need NVH control at the front diff mount (the whole drivetrain is basically a solid unit that's rubber mounted, instead of several discrete pieces that are all independently mounted) it also means less flex in the system and thus better throttle response. 

I've built a few cars with C5 parts.  I kept the stock wheelbase but shortened  (had a machine shop do it) the torque tube to move the engine rearward.  Also made a fuel tank that wrapped around the torque tube to keep the weight low and centered.  The frame made from aluminum tubing with aluminum plate welded it.   The trans tunnel ends up very wide.  Here is picture of one of the builds. 

Keith Tanner said:

Pete. (l33t FS) said:

Keith Tanner said:

Another advantage is that drivetrain torque is not transmitted through the chassis. 

It isn't?  

...No, I suppose it isn't.  The torque resolves through the torque tube, unlike a power plant frame that is necessarily fairly weak in torsion.

(And it is kind of weird to use the Mazda term for that... the earliest I know of that device is the last few years of C3 Corvette.  All C4s had one)

4th gen F bodies had one too. 

So you've got the twist from the engine, but at the back you also have the rear end trying to torque its way upwards. The Miata PPF flexes in twist so it doesn't do anything to restrain the engine, but it does locate the rear diff and the transmission. That takes a big bending load out of the chassis. Since you don't need NVH control at the front diff mount (the whole drivetrain is basically a solid unit that's rubber mounted, instead of several discrete pieces that are all independently mounted) it also means less flex in the system and thus better throttle response.

The late C3 and C4 had no trans mount or diff mount, the front of the diff and the rear of the trans were mutually supporting.  Mazda liked the idea so much that they used it for the Miatas, FD RX-7, and RX-8.  (It's a good idea if you have room enough in the trans tunnel.  Miatas made good use of that in giving strength to an open-top tub, and anything rotary is going to have a huge tunnel anyway since the transmission sits so high up)

4th gen F bodies, being solid axle, had a torque arm, but they still had a transmission mount.    The suspension was very similar to that used by the T bodies, also known as Chevette, and IIRC the Opel Kadetts from the 1960s also used a torque arm.

So did prewar Ford trucks, IIRC...

Somebeach (Forum Supporter) said:

Specifically a c5 torque tube and transaxle set up.

1. Benefits and drawbacks of a setup like this?

2. Could you swap this to any ls type engine for a junkyard style swap? 
 

3. Is the transmission different from the normal 4l60e or t56? 
 

 

 

1. Benefits and drawbacks of a setup like this?

• Allows better weight distribution mainly.
• Makes any clutch work a PITA. Its way up at the front.
• You have additional maintenance with the dampers in the tube.
• Labor for anything to do with the driveline is higher.

2. Could you swap this to any ls type engine for a junkyard style swap? 

• Mostly yes. I've seen a ton of people swapping various LS engines into c5's over on corvette forum. Slapping a ls2 or ls3 is common when your ls1 pops.

3. Is the transmission different from the normal 4l60e or t56?

• Different in that you can't just slap on in there. If you're looking for a core it makes it a bit more challenging. If I had a dollar for every time I clicked on a part that a Camaro owner didn't label which car it came from...

Been there done that got the T-Shirt....

• Curtis is pretty much spot on about the trans, they are basically a standard T56 or 4L60 with a few minor changes to accomodate the shifter location.  As I recall the CTSV and C5 have the exact same guts, the shifter location and front and rear faceplates are different.  Viper stuff is beefier, F Body stuff is wimpier.  The rear diff is a separate unit with separate oil, as such its a pretty long system to use for mid-engine.  
• The hotrod setup is a TR6060 out of a C6 Z06.  I should have  done that, couldn't keep a T56 or rear diff together to save my life.
• The 4L60s are wild, the torque converter is at front of the trans not the back of the engine - makes sense really when you think about it, but looks a little goofy.
• The torque tube definitely could be shortened or lengthened within reason.
• The whole thing is packaged up pretty nice as long as you don't mind cutting up the rear floor of whatever you are trying to fit it into.  Would be easy to fit into something pretty low/small engine bay. 
• They are not that bad to work on despite the unconventional packaging. Jackstands in the driveway, clutch is a 4-5 hour job once you know how to do it.  
• If I was going to swap one, I would buy a complete C5 - they are cheap enough - and use as much as I could from the system.  I would definitely want to try to keep it as a unit as shown in your photos.  All the brakes and suspension stuff is real good and with the factory leafs you do not have many connecting points to the swap body.  
• There are only 3 motor mounts.  One in back on the rear diff and 2 in the conventional location on the engine.  Whether or not that matters to you is up to you.

Any other questions?

In reply to jmc14 :

That car looks great. Did you buy a whole corvette for a donor? Or buy it part by part? 

In reply to 93gsxturbo :

I am trying to visualize how the engine actually links to the torque converter in an auto if the torque converter is in the back at the transaxle. 
 

What does the driveshaft hook at the engine? 
 

Also thanks for all the great info in this thread. 

Somebeach (Forum Supporter) said:

In reply to 93gsxturbo :

I am trying to visualize how the engine actually links to the torque converter in an auto if the torque converter is in the back at the transaxle. 
 

What does the driveshaft hook at the engine? 
 

Also thanks for all the great info in this thread. 

Flexplate and starter are in their normal place at the back of the engine.

There is a little splined coupler that bolts to the flexplate on the engine.  It basically takes the place of the clutch.

This splined coupler accepts an input shaft that looks just like a manual trans input shaft.

The rear part of the torque tube has the same mating part that the back of an engine would typically have to drive the torque converter with another flexplate.

https://www.ebay.com/itm/225869155308 has some good pics.

https://www.ebay.com/itm/134711979274 - the front flexplate.

In reply to 93gsxturbo :

Thanks. That helps a lot.
 

Did you do a swap with a corvette torque tube? 
 

Also with the removable bellhousing would you be able to get away with a smaller/easier adapter plate if you wanted to mate it to a non-ls type engine (not that anyone would want to, but just learning here) 

I have not swapped a C5 driveline, but I have had my C5 manual trans driveline apart down to the last snap ring, synchro, and pinion gear about a dozen times so I am I pretty familiar with how it all screws together.

Swapping the auto trans C5 or C6 driveline to another engine would be straight forward.  

You would need a custom bellhousing.  As long as you maintain the same engagement between the torque tube input shaft and the little coupler, every other dimension could be open to interpretation.

You still need provisions for a starter, there is no provisions for a toothed flexplate in the rear flexplate that the torque converter couples to.  Not saying you couldn't make that provision, but it would be a pain in the dick.  

I would modify the little adapter that bolts to the back of the engine flexplate to fit the bolt pattern of the crankshaft of your desired engine.  Its the little item with the internal splines bolted to the flexplate in the listing below.  You could also have one whittled out of billet since that spline is a known published item and would be easy to cut with an EDM.  I would still want one to reverse engineer to get the fits, offsets, clearances, etc correct

https://www.ebay.com/itm/325704516901

You would need some means of controlling the auto trans.  This is easy enough, plenty of stand alone options.  Let your wallet make this decision. 

Using a C5 or C6 manual trans driveline on a non-Chevy engine would be a bit more of a trick, if I was going to do that I would keep the OEM bellhousing because it has provisions for the hydraulic throw out bearing, and get a bellhousing adapter and custom flywheel made up, keep the Chevy input shaft on the torque tube which is standard T56 dimensions.  Any custom clutch for whatever motor you have to a T56 would work with minimal headache.   

It's worth noting that when the C5 drivetrain added footwell area by taking the trans out of there, it added to the space needed between the seats.  I have my project where guys ask why I didn't use a C5 transaxle when they're so slick, answer is the body is too narrow there to accommodate two people's butts and a transmission too.  You can see even from outside the car how a C5 is wider than the previous gens in the passenger compartment.

Also the C5 "transaxle" is a lot like just a conventional drivetrain with the components in the same order but with the fore-aft spacing different.  It is not like a traditional-style Pantera ZF or Mendiola with an engine output/trans input shaft running under the axle c/l then the trans is behind, with its output into the diff running forward again essentially off the countershaft (note the countershaft in that case is always under torque and unlike a conventional transmission that locks the mainshaft up at final drive and bypasses the countershaft, final is rarely 1:1).  Net effect of all that is, a mid-engine car with the C5 trans is going to have the engine further forward than a mid-engine car with a traditional transaxle, which somewhat defeats packaging advantages.

I just stumbled on to this site and found this dialogue, Great Stuff. I owned a 1998 Corvette and put 140,000 miles on it. I had two engines, two 6 Speed trans and 2 rear gear sets oh and 2 Torque tubes. I did all the work myself in my 2 car garage with 2 floor jacks and 4 Jack Stands. Oh and two PCMs actually 3, I updated to a 2000 PCM. I always admired the transaxle design and the suspension with the cradle etc. I had to do a lot of dropping the rear end to fix the clutch several times. I always thought that rear assembly should used in some older cars.

I recently saw a really ruff 1983 El Camino, and that has me thinking. Would that Transaxle and Suspension be a  cool update to the old ELCO????

Dennis