944Hybrids: 924/944/968 and 928 V8 Conversions
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For the benefit of 944Hybrids users there are two search functions available for you to use.
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Sharkey's 944 corvette t56 swap thread Empty Sharkey's 944 corvette t56 swap thread

Post  sharkey on Sat Oct 10, 2020 11:43 pm

So i figured id start a thread on my upcoming project on my 944, and thats to swap to a corvette t56 transaxle and torque tube. my goal here is to give a detailed account of what it takes to put the corvette driveline into the 944. i have yet to find a detailed thread on this swap start to finish, there are multiple cars running around with the swap, and other still in progress, but info seems a little scarce. obviously there are multiple ways to go about this swap, this will be my take on it, but ill try and detail other options along the way.

first off, my engine swap is a little different. for those not familiar, im running a chevy 2.2l ecotec, and right now im around 500 whp. i have a swap thread HERE and a photo gallery here . some may question why i need a corvette transaxle with this engine, surely the AOR transaxle with AOS final drive can stand the power from a turbo 4 cylinder, and its done well so far. i drive it pretty easy, no launching, no burnouts, etc. well my plans with the car have changed, originally i built the car for street and with the intentions of getting into track days, but after 5 years i have yet to get on a road coarse. my local track doesnt do open lapping days, they do private track rentals to groups, and unless you have an in (which i dont) with a group your out of luck. my next 2 closest tracks are members only facilities, and again, if you dont know a member (or have $50k for a membership) your out of luck. so with that, ive decided to switch my focus to drag racing. a bucket list thing for me is to compete in a drag week style event, and i figure instead of building another car for that ill make some changes to the 944 and do it in that. my goal is a solid mid 10 second stick car.

so that being said, my swap will have a few differences than with a v8. all these differences will be from the front of the torque tube forward. my engine currently is mated to the porsche torque tube, the torque tube flange is in the same spot as any other 944, so the torque tube and transaxle will end up in the same location on mine as an ls swapped car. i will detail my clutch and bellhousing setup, but if you use this as reference for a v8 car everything you use here would be factory corvette, clutch, flywheel and bellhousing, and will all bolt together as it was designed to.


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Post  sharkey on Sun Oct 11, 2020 1:20 am

so the first thing is selecting a transaxle and torque tube. i ended up being given a 2005 transaxle, which isnt the best option, but more on that later. here is some info on some options

c5- the transmissions themselves are mostly the same from 97-04, however there are some variances with the diffs. all manuals came with 3.42 ratio, automatics came with 2.73 or 3.15 and are interchangeable with manuals. the cases have been upgraded through the years, in the c5 era there were single rib and 3 rib cases. the 3 rib is often called a z06 diff, the c5 z06 first got this case, but around 2001+ all corvette manuals got the 3 rib case. all c5 transaxles mount under the rear of the diff

c6, 05- this one is a bit of an oddball, the transmission is the same as a c5, and the diff had the the new mounting ears off the side covers. these diff cases are known for being weak, the new style mounting ears changed where the load is put on the case. this shouldnt be a big issue in a 944 swap as most wont use the mounting ears, however it would be best to avoid this diff. this is the diff im using, however ive designed a brace kit to hopefully fix the weak points. z51 models got a transmission oil pump and a cooler.

c6 06-07- this is the same t56 as prior years, however the tailhousing was changed to a stronger design to coincide with a new diff case. the diff case got completely redesigned to address the weak points. the diff and tail housing from these transaxles can be swapped to an older transmission, but the tail housings are getting hard to come by. the z06 models got an upgraded 30 spline mainshaft in the transmission, a 30 spline pinion gear in the diff, along with a stronger passenger side output shaft and diff side gear. its common to swap the shaft and side gear into previous diffs. the z51 and z06 got a trans cooler system, and the z06 got a diff cooler.

c6 08-13- 08 is a new transmission, the tr6060. sharing the look of the t56 is about all thats the same, these are much stronger transmissions. all models got a 30 spline mainshaft, all the gears are physically larger, more refined syncros, etc. the diffs stayed pretty much the same.

c7- this is a tr6070 7 speed manual. these got an electronic diff. i dont have much info on this setup, i had no need to research them.

torque tubes

there are multiple lengths of torque tubes for manuals (autos wont be discussed)
c5- 54.375"
c6 05-07- 55.875"
c6 08-13- 55.75" (not 100% on this length)
c7- 53.5"

the c5 has 2 different manual trans torque tubes. 97-2000 had 10mm bolts in the driveshaft couplers, 2001+ (often called the z06 torque tube) got changed to 12mm bolts.

the c6 torque tubes changed with the change to the tr6060, the tr6060 was longer so gm shortened the torque tube. some people claim the c6 z06 torque tube is lighter, i cant find much info on that though.

i can confirm the torque tubes between 97 and 07 are completely interchangeable. from what i can find, the torque tube 08-13 is the same aside from length, so it should bolt right up to any earlier transmission. the c7 torque tube was something i was interested in because of the length, however i wasnt able to confirm it would work with the earlier transmissions. i suspect it would, the bellhousing on the rear of it looks the same, and everything uses the typical gm 26 spline input shafts.

now here is some info on driveline important lengths

transmission length, 97-07- 19.315"
diff length from mounting face to axle centerline- 4.600"
total length of transaxle, mounting face to axle centerline- 23.915"

944 torque tube flange to axle centerline- 77 3/16"
c5 tt to axle centerline- 78.29"
c6 early tt to axle centerline- 79.89"
c7 tt with c5/early c6 t56 to axle centerline- 77.415"

going strictly off the measurements, the c7 tt and t56 transaxle seems like the winning combo, and if i could have confirmed it would work i would have gone that route. being the price difference between a c5 and c7 tt ($200 vs $800) i decided against experimenting. the less than 1" longer c5 driveline will work just fine. for most doing a corvette driveline, the c5 stuff is a good choice, especially if you can get it all from one car. another option would be c5tt and 06-07 transaxle for the stronger diff/tail housing. even stronger would be the c5 tt and tr6060, although this is an untested combo in a 944. imo, either c6 torque tube is unusable, both are going to push the axles back too far.

gear ratios

base and z06    z51      zr1
1st-  2.66        2.97     2.29      
2nd- 1.78        2.07     1.61
3rd-  1.30        1.43     1.21
4th-  1.00        1.00     1.00
5th-  0.74        0.71     0.81
6th-  0.50        0.57     0.67

common transaxle upgrades in corvettes

torque tube couplers- inside the torque tube are 2 rubber couplers. while they are strong and offer some dampening in the drivetrain, people often upgrade them. solid aluminum versions are offered as a race part, and aluminum with urethane insert versions are offered for cars seeing street use.

driveshafts- with high power and rpm some have found the driveshaft to flex inside the tube. larger aluminum driveshafts exist, along with carbon fiber.

transmission upgrades

syncro rings- all corvettes got fiber rings, however the aftermarket has carbon/kevlar rings that hold up better with high rpm.
syncro keys- the stock keys are stamped steel, and a failure can be catastrophic. aftermarket billet keys are a wise upgrade for at least 1-2 and 3-4.
shift fork pads- another cheap upgrade is to change the plastic fork pads to aftermarket bronze ones.
3-4 fork- other versions of the t56 have an aluminum 3-4 shift fork thats prone to failure when banging gears, the upgrade is a steel fork. luckily, all corvettes have this fork.
gearsets- there are multiple aftermarket gear set options from just changing 5th and 6th to ratios better suited to high strung engines, to full straight cut face plated gears, its all out there for the t56.


all corvettes have a clutch style limited slip. eaton has a replacement clutch style diff, and wavetrack makes a torsen style diff
output shafts- high high power and sticky tires corvettes are known to break outputs. the c6 zo6 passenger side output and side gear is a common upgrade. there are multiple companies making output shafts and side gears out of exotic materials
gear ratios- corvettes have everything from 2.56 to 4.11s available. factory 2 series diffs require a special "thick" gearset to use a ratios 3.15 and up, however this wont apply to most as 2 series ratios are auto only. it seems most people argue over whats better in a corvette, 3.90 or 4.11.

transaxle braces- several companies offer braces to go from the front of the transmission to the diff to prevent the transmission tail housing from cracking. this is a wise upgrade for anyone, although if you dont plan on high power or racing may not be needed.

here is my choice of setup, a 2004 c5 torque tube and a 2005 c6 z51 transaxle

Sharkey's 944 corvette t56 swap thread ACtC-3cDFjXA6dNg_fo-N_sJVB5duEibkrv2BW6TJ5YsPzXSmGAKXsLv51M2oK_LbHOUHZF7DTF2u_drDr_pXAwzmym-KanhdzpiKIB1Fru1qkzQzCT8QVfdhmOQg6YDwFIw9RMt-T3y_1oAoy9PCkjSDdqf=w1605-h903-no?authuser=0

i split the transmission apart for inspection and some upgrades

Sharkey's 944 corvette t56 swap thread ACtC-3cdVe1Pb9qN9DUN2c8Z_vYbd-LRhsHvXGbL3g8uAVXykcqalOUDWM_0_H2bT7lHWJTt-1kcXerXYGzszLspRxvw863hzhYBgOT9RWvjNtSkfvGVjNhpR6FDf23xsRB0dAI4QOsAx7hIJNDt8SjNdc1R=w1605-h903-no?authuser=0
Sharkey's 944 corvette t56 swap thread ACtC-3ebtCLmJROMEJ37R1-Dko9rr-V-4jdl-sSyAKqxYa0QzuGgMqKpOy_qw3Z4xT9mj7el70QnSdFM2fdwCUpbWwHaP3w8wuYaUYN-0MogEgoIcpVe0m9BD7w7jirU-Jmq3ASYVEDjGe24a7l7E5gjRTt1=w1605-h903-no?authuser=0

billet keys vs stamped keys
Sharkey's 944 corvette t56 swap thread ACtC-3cKJ0u06w5revC0mt09AVqUBoY18xZd7f4S4jtnq1Lq_5HX0iBq8frU-QalGy6h3zSjhPf0kkPnCPk7YEsPznVTs_1Bk_Cf4Kb4bGJOvN9kSX6QB_ucNnxiejyzZjhkRdYq4UVPMYvdzHPMuPoKTErr=w509-h903-no?authuser=0

bronze fork pads
Sharkey's 944 corvette t56 swap thread ACtC-3eM7Hx7hvWNa3ruzw7gPZB3NRNdFcwIQCqst0kfsL4qoqKF1whkxkPzr5k9_t-z4pZMtqwtvoLSXqoNrgSweD0Ta202VruSGaG9thLICFgZ3w7VBbFodmqFgnKdHMqxEUx27uCDw81-oMGlZH8Sb3Td=w509-h903-no?authuser=0

also pulled the diff apart for a 4.11 yukon gearset

Sharkey's 944 corvette t56 swap thread ACtC-3cAavBBjmNk5_UcGIGUTF4HSd679o3pXO8d1HnUUBxdLbUT-JbWyYFA9IduTahzYQG95jPR-mbdStwfsbAxg_jcLSlAbQ0j8g_rO1Ctb6vTmfxFZZ_EPLd5sHY2hWbrnJEKiAIbSSnQ2kZj0-8FAGWQ=w1605-h903-no?authuser=0

this is one of the outputs often upgraded. i left it stock for now.
Sharkey's 944 corvette t56 swap thread ACtC-3dApGzGnp9ae3I5nHV4qgDsPVwpObUEdQ-Kyr0VydbuW5xZScvVmmqfJYnGacYbGHJiqHgmi-lmHEseHpwGaXtFLs2vmAscq1oBxjAL3WCK_Ky6gPabGHzqjBTvayRp9lcE-mUMHYBuIYmulC6vZyEY=w1605-h903-no?authuser=0

and the new gear set
Sharkey's 944 corvette t56 swap thread ACtC-3cjVUNWpayfkq2Uz3IHSGocDU3l0uWIa_UG8ZNcc32hU9j6i1ZP48NhcGVO9QrTjbxPgT9iRuAfZNpshSPt7T5nM8__CUwMqI0BC_Kb3DN-BZN0bXqE1aoqIfBtOe9gaT9uUtmM3kcUx41CpbuhC053=w1605-h903-no?authuser=0

torque tube
Sharkey's 944 corvette t56 swap thread ACtC-3fClthn34fMQ7kKANhq3Ac2WXlYIp4aLlAUKEWWjw9kgmbAhqji7TkhdLRzdcRMmhQXbTZMV875k78eWH6glYe-7gsAt4HzKRK2Oig_H22G5V5T6Lhq3VuAKwFQtG5zUPnQObJKK079OYhi61gEpPcH=w509-h903-no?authuser=0

all together

Sharkey's 944 corvette t56 swap thread ACtC-3d21ZItAPvYPwIMqbjTrMQHNEuxknWTdMusPklG-xBQb1Z7sI8dIvlyuuWxf1rCcb9tDzdzNQNwUAmOoWW4F7XICU2uEI8YjOmM92Vap9RW5ZXXjUwnDZI42GZaYJBKtWel0si1ipu4bWGxkMgmHmJ_=w509-h903-no?authuser=0


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Post  sharkey on Sun Oct 11, 2020 2:32 am

with the corvette transaxle wanting to occupy the same space as the torsion tube, a major change here is needed. no matter what you do you will need to cut a section of the floor under the back seat, and you will be doing a rear seat delete.

option 1- swap to corvette
going this route you remove all the porsche rear suspension and put in the corvette cradle, knuckles, control arms, etc. this route requires a fair bit of structural changes to the back of the car to mount the cradle and upper control arms.
pros-easy to mount the transaxle
-uses stock corvette cv axles
-better rear suspension design
- better brakes
cons- complex structural work
-very wide track width, needs flairs or widebody
-different bolt pattern than front

option 2- modified torsion tube
this route removes the torsion bars and requires full coilovers. the torsion tube is cut in half and a U is welded in the middle to allow the transaxle to pass through. uses the stock trailing arms, brakes, etc. the transaxle is generally hung from the top.
pros -less fab work
-mostly uses factory parts
cons -requires custom axles

ive decided to retain my factory rear suspension, to me its the most logical choice. so skipping over all the fab work (im not there yet, ill show what i do in detail later) the next big thing to sort out is axles. going from the corvette transaxle to the 100mm type 2 flange can be done in several ways, depending on how strong you need it.

1)all out
-930 style flanges for the transaxle. these are common for corvette axle upgrades. made by geforce, drive shaft shop and other. i priced the geforce ones, they were $800usd for the pair
-930 style cv joints. pick your brand
-outer adapter flange. your going to need to convert the outer stub axle from 100mm to 108mm bolt circle (type 2 to 930). im using an adapter from PRD racing products, although drive shaft shop and lindsey racing use the same sort of thing for their 944 level 5 axles

-930 flanges for transaxle
-108 to 100mm adapters to bolt to the 930 flanges
-use type 2 (factory size) joints and a shorter axle

3)fusing corvette and porsche axles
-corvette inner cv joint. the factory corvette c5/c6 axle shaft/joint use the same 28 spline as a 930 cv joint. some corvettes use a tri-lobe inner plunging joint while others use a plunging 6 ball setup. wither will work, although id assume the 6 ball is stronger. *this may not work non oem corvette axles, my parts store replacements were a different spline size*
-100mm to 108mm adapter for outer
-930 cv joint for outer
-28 spline 930 axle shaft

im going with the 3rd option. i feel the 6 ball corvette inner joint will be plenty strong. the only thing i dont like about this (any of it) is the adapter on the outer stub shaft. it would be so much simpler if there was a 108mm (930) flanged stub shaft that fit a late 944, but to my knowledge this doesnt exist (if it does please post it). ive decided to use empi parts to do all this. im using a 930 race joint for the outer, and will be using empi axle shafts once i determine what length i need to order.

here are the adapters
Sharkey's 944 corvette t56 swap thread ACtC-3eK75do5rNHQHG4V9UBL1pjGU0lcMO0-qaeweVyYJw7dUVC4gZNM-p8uEpllVdfqx8sbInEm5H9-GDP3IGqVDwV4ILthuF3SYh-hf5d7elhkXTpg80fFFba-11HvAuHvVFZUdIdC287F9EsuiTcOKhc=w1605-h903-no?authuser=0

outer cv joints, empi 930 race joints with chromoly cages, small 930 boots, hardened steel boot flanges and spirolox snap rings
Sharkey's 944 corvette t56 swap thread ACtC-3fCigCsZSyh0VKrQWqqxs1KaGu4raD0SoG1GNztG6pDuArFnAvbnPJy3FQY1Ge5WIiVW7JDttALmdjHopPxBgzERP_AvaZvWjmJzINVJqeBWRcdVD2aObMhTrpbWls_FmKcMWjWUH-lx9h9eMsXBaX1=w509-h903-no?authuser=0

corvette inner joints taken apart
Sharkey's 944 corvette t56 swap thread ACtC-3cwOHDGDTmyOzMzpqAJWVTs65qYHmlNFX9ulFNakR9ENvfY571Rlonwzzub2tPoBAmFxq_FcimUIvEhwiRBsHJxLJRv940yWlQLQ879TRzfviv7mutFkiIRjR-_drOAwX-wY4uYQERgtpg1opeU7J8I=w1605-h903-no?authuser=0

Sharkey's 944 corvette t56 swap thread ACtC-3f79_cLD-FCTr2yxPbFb0slnf_6CIX71Yz63Bta-TlyMgl9hpnFSgs2uZGXfN_yHnod8-Q2__2G8fg9nK9txeZxO9W8KJpeVZFvAUTsyWQUrVV3qvogSwDgN9fYs4XggVVP9swH_AWhNNYofNkBtQTW=w1605-h903-no?authuser=0

Sharkey's 944 corvette t56 swap thread ACtC-3feX_uFi7vB67lea25oh2XDK-xB67RdNtJJoyMF4BE24ZOKpjOf6qcGEwk1FVnvzZr4MtyxFCUipd1O_BuKNhKxEU_PBhGzet53iDNpmU-k-JfaMUKseJq0guH1r_oA8A1Hu0pKPmDglqPtUW69PrDL=w509-h903-no?authuser=0

this is about all i have to show right now. my car is currently sitting in my showroom at my shop for safe keeping while i wait for some more parts. currently im waiting on my clutch and flywheel to be made and shipped, and waiting on coilovers to ship. once those parts are in my hands ill be stripping the interior, removing the old drivetrain and start cutting the car up.

Sharkey's 944 corvette t56 swap thread ACtC-3cyeecWHJ_cI68-7Jv4WhNOeU4cup6Ot54q9LcDPtcJcpjWNC_ir8qJTtKW5Pl5_1Lw-1EItNe0l0BEjiYFVOcfp81fIcXElr3pxZlaIovMgfVnWbLNl6q2OzZyyt08it3g0Cqe7X-IvVZtkohwae0K=w1605-h903-no?authuser=0


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Post  Myporschels on Mon Oct 12, 2020 6:54 am

Thanks Sharkey for this! I too have been searching for some detailed info on this swap. In my case, i have a fresh LQ4 6.0 ready, but have been struggling with the set up. This summer i found C5 transaxle, TT, and complete rear end including frame rails neatly removed from the Vette. So my plan is to fabricate those into the 944 and bolt up rear end, then work forward. Intend to find Corvette or Camaro front end as well. What are you seeing with the 944 tunnel? Will we need to split and widen it?

Keep the updates coming.

MikeSharkey's 944 corvette t56 swap thread 20201010


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Post  Geoff Daniels on Mon Oct 12, 2020 7:21 am

Thanks for the great info and taking the time to document your work. I have a 1986 951 that I put a hopped up LS6 in several years ago. I kept the original Porsche turbo (not an AOR) tranny at the time but have been considering an upgrade to the T56. I was able to acquire a T56 transaxle and TT from a friend that had a mishap with his 2001 Z06.

I will definitely be following your progress.


Geoff Daniels

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Post  sharkey on Mon Oct 12, 2020 12:10 pm

Myporschels wrote: What are you seeing with the 944 tunnel?  Will we need to split and widen it?

i dont believe the tunel itself is that much of an issue. yes, things will be tight, and the area around the shifter may need to be cut out, but i dont believe it needs a complete redo. im planning to look at the feasibility of moving the shifter from the side of the torque tube to the top, or at least a little farther up the side of the tube, this would help with tunel clearance, and my goal is to get the shifter in the factory spot in the console.

under the back seat area, thats a different story. i have 2 thoughts on this and im not really sure what way to go. can either cut the smallest amount of floor out to clear the trans, or take the whole section out under the seat and make a nice flat floor that goes from the front of the rear seats area up to the trunk floor. this would make finishing and carpet much easier, and would look better imo. ive gotta see what im dealing with once its all apart to decide what i wanna do. unlike what some people have done, i do plan to keep the entire trunk floor, imo there is no reason to cut it out.


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Post  Myporschels on Tue Oct 13, 2020 10:01 am

Mine is automatic, so will still have to address shifter console area. By the way, i have a manual C5 shift lever if you need it... i plan to cut out entire back and rebuild with roll bar assembly and then area for fuel cell. Glad to hear that the TT should fit in tunnel


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