dprantl

We could use this thread to measure and compare transmissions to determine what could fit where and with which modifications. Rob, could you take some more measurements of the GTS 5-speed? xcshop, could you do the same with a T57/tremec, assuming you have one lying around?

Dan
'91 928GT S/C 475hp/460lb.ft

Vilhuer

Yes with enough big hammer. Do you want to keep rear seats?

xschop

I posted here because these guys know their stuff when it comes to transaxles. I already have the drawing (although not programmed into my CNC yet) to mate the C5 differential on the back of ANY AISIN 5-speed using the Jeep/Toyota 4x4 tailhousing.....This setup will go into the 928 with not too much fuss as I will convert a 928 automatic later because I know where one is sitting with a bad motor....Anyways here is what I am trying to find out so that this same C5 differential and Aisin Tranny can be configured diff. before tranny to fit the 944 without having to cut the floor pan.....
I'm just not sure about the shaft arrangement and gear/shifting mechanism inside the Aisin boxes if reconfigured this way....

http://www.gt40s.com/forum/gt40-tech...transaxle.html

Here's the 944 axle to Torsion tube dimension that would require a longer adater tube and shaft between the Aisin tranny and C5 differential. The Floor pan would have to be modded and a shorter Torque tube would be a plus....



And to answer the 928 G28 tranny into the 944 Question......
The Early 928 Torque tube is longer than the later one and is only +- 1/4" differece between the 944 TT/BH flange and Audi Box axles....But you have the stinky 944 torsion tube to mod (which can be done but alot of work)



THE ONLY DIMENSION I DO NOT KNOW IS THE 928 AUTOMATIC Torque Tube dimension. By the pictures up against the longer 5-speed 928 Torque tubes from other threads here, I have no doubt that it could be used to swap this Aisin 5-speed/C5 trans combo into the 928 with another adapter and coupler up front.....

axis of evil

DON'T USE A R154!! This box is NOT bulletproof, Real bad synchro ring wear problem on 1st gear, can be fixed at a price, but when you do, you are still left with the worst shifting box that Toyota ever put into a car , There are 1928 Studebaker trucks that shift smoother than this!
The first car they used it in was the Mk 3 Supra, when it replaces the W50 series, I think Toyota was indicating a problem when they reverted to the W50 series for the NA Mk 4 Supra's. (The R160/161 Getrag 6 speed used on the TT Mk4's would probably be too big for your purpose) Even the later versions used in the 1JZ/2JZ Soarer and chaser's (Na and TT) are still ugly primitive shifters.
Fully rebuilt, and new out of the box, Very notchy shift.
There are better gearboxes out there.

Landseer

89 Auto Torque tube, flange to flange, just a hair less than 46 1/2 inches
Central shaft is that number plus about 7 5/8 inches

84 Auto TT is exactly the same flange to flange measurement
Its got a bit more shaft length IIRC due to circlip set up.

xschop

Axis... you are correct. And I was contemplating the r154 before I discovered the lower C5 Automatic diff ratios of 3.15 and 2.73 LSD which would be perfect all around ratios for the 928 and 944-V8 when mated to the Newer Aisins found in Colorado, Canyon, Hummer H3, and the close ratio Pontiac Soltice. The C5 diffs that are mated to the Clunky (Read Poor Synchros) T-56 are a little high R&P ratio ( 3.42, 3.9, 4.1 etc) for my taste...Although there are upgrade synchros and gears for the Toyota R-15x boxes, The Newer Aisins have Triple cone synchros from the factory. I may just be getting a Hummer box or Colorado box with the 4x4 housing already installed after all since I just acquired my C5 2.73 LSD differential. What's unique about the C5 diff. is that it mates to the output shaft and slides right on and off because the R&P is hollow and the preload/backlash is adjusted in it's own carrier located inside the differential housing itself. R&P ratios are pretty much unlimited for the C5 Diff and that opens up many possibilities with all the various Aisin 5-speeds listed with their various ratios.....

AX15 - 3.83 2.33 1.44 1.00 0.79
AR5 - 3.753 2.26 1.37 1.00 0.729
MA5 - 3.753 2.26 1.37 1.00 0.729 (Colorado/Canyon/Hummer H3)
MA5 - 3.75 2.26 1.51 1.00 0.729 (Solstice/Sky)
R150 - 3.83 2.062 1.436 1.00 0.838
R151 - 4.31 3.32 1.52 1.00 0.83
R154 - 3.25 1.95 1.30 1.00 0.75
R155 - 3.954 2.062 1.436 1.00 0.805
NV1500- 3.85 2.25 1.48 1.00 0.80
NV3550 - 4.01 2.32 1.40 1.00 0.78
Aftermarket gearset by OS Giken for Toyota R, GM/Isuzu AR5 and Jeep AX15: 2.701 1.614 1.215
Aftermarket overdrive gear for R154 by John Doward - info@vcsystemsonline.com: .66

xschop

BINGO......By my calcs, for the 928 Auto to swap to this 5-speed/C5 , the Auto Torque tube can be re-used......

BC

Aisin is the transmission supplier for Volvos right?

Doesn't sound like a good plan to Aisin -

The 928 5spd needs the update - the 928 automatic IS bullet Proof.

xschop

I test drove a Pontiac Solstice last year and that was the smoothest shifting car I have ever driven. The Toyota Supra guys are now installing the Solstice tranny in their MK's. The input output counter shafts are the same arrangement as the R-15x's and the gears are W-I-D-E like the r154's that make them take alot of torque like some of the 5-600 ft/lb turbo'ed Supras, The synchros sucked from the factory, yes, just like the Early 928 boxes. Another problem with the 928 box is the long alloy case that flexes from heat expansion when run hard, the gears and bearing suffer as a consequence. The Aisin boxes have a sandwich plate between the casings.The R154 and other R15x's happen to have a thick steel sandwich plate and can take more torque and high heat....FYI

axis of evil

there could be something in these threads that may help you.

http://www.lextreme.com/forums/showthread.php?t=11188

http://www.jeeps-offroad.com/f41/eng...housings-4740/

Hilton

Bump - ran across this thread while searching for info on diff's.

How far did the investigation go? Did the 928 member get as far as a conversion using the Aisin 5-speed manual?

Presumably this mod would also work for a 928 manual - with an auto torque tube.

No big deal if not much progress has happened - I just figured this is one of the more promising looks into replacement trans' I've seen in a few years.