xschop

What is the front TT mounting flange face to axle center distance on the 928/G28 ? Thanks

Rob Edwards

As a rough measurement I get about 19-7/8". That would be 504 mm, so maybe it's an even 500 mm?

xschop

Big Thanks. Is that from an Early or Later 85-up manual transaxle?
Very interesting.... Doing research for a 944 TA upgrade for my 5.3l V8 swap and found that the 928 TA may be made to fit past the 944's Torsion Tube... the 944 TA Torsion bar center to axle centers is 16.5"

jeff spahn

Are you saying you're putting a 5.3L V8 in a 944 and want to upgrade the 944 TA to a 928 TA?

xschop

Chevy 5.3l is already in and plumbed to the TT and NA tranny. I am doing research on a few different 5 speed boxes to mate to a Corvette C5 differential. So far I am leaning towards a r154 because it is bulletproof and have discovered that it would be easier to do in a 928 because there is no Torsion tube to deal with like the 944, hence the 928 transaxle dimension question. I know from reading here that the later had improved synchros, but these are not as good as the newer trannies (TKO) and newer T56's in the newest Corvettes, but the T56 is way to big and the older ones that still demand $2K have poor synchro design.

Rob Edwards

That was on a '93 GTS box, but I'd think that measurement would be the same for everything back to 1980, if not 1978.

xschop

Thanks Rob. I wasn't 100% sure because I read here and saw the TT dimensions between the Early and Later 928 Torque tubes, the later being 30mm shorter. I'm surprised someone hasn't done an upgrade swap to a newer tranny on the 928 since it would be an easier swap than the 944. Thanks again.

James Bailey

For those reading along..."made to fit past the 944's Torsion Tube... the 944 TA Torsion bar center to axle centers is 16.5" ...." the rear suspension on the 924-944-968 uses torsion bars for springs that run from side to side (as does the 911) that large housing "torsion tube" limits what you can do !

Lizard928

dont forget though that the 924/944/968 all use audi based trannies with lard bellhousings on the front of them (for clutch/torque converter from trannies origonal use). The 928 manual does not. So it will fit. But you would need to shorten the TT and subsequently the internal shaft (or have a new one made).
Also keep in mind that the audi based boxes have the halfshaft connections in the middle where the 928 is at the rear.
Also look at the G31 (79/80 931 transaxle) they do have poor syncro design, but are VERY stout boxes that will bolt right in place of what you have. You will need to weld some ears onto your torsion bar carrier, or find a 931 torsion car carrier to use.

xschop

exactly.... if you are a 944 owner and have done tranny work, you know that the audi box has another 10-11 inches of torque tube sticking out past the torsion tube before it mates to the audi bh flange, this is perfect for fitting in a Tremec T5 or TKO (maybe) and mating it to a C5 differential with multiple Gear ratio choices.

xschop

Little update, I found that the Automatic C5 Differentials have 3.15 and 2.73 R&P's. I have a 2.73 LSD on the way and when mated to the Aisin 5-speeds puts the tranny flange to axle center at 22"
What this means for the 928 guys, is that the 928 Automatics can be adapted to this set-up since their Torque Tubes are shorter than the G28 5 speed TT's. I have been talking with a 928 member here about doing these trannies in converted 928 autos. I will be posting here what I am doing for the 944 as the tranny to C5 adapter and extension shaft will be the only difference between installing one in a 944 or a 928. If someone in the OKC area would like to do a 5-speed swap to their 928, I will be glad to collaborate and share knowledge.

Vilhuer

It has been done. Its not direct swap as TT center shaft meant for '78-80 MY G28.03 tranny will not fit into '80-95 later style tranny input shaft without modification.

xschop

What is the shaft diameter and spline count difference between the Earlier and later Torque tube shafts? I have access to spline cutting equipment also and will make my own shaft and coupler. The other member here has a source for custom shaft building as well. But once I can confirm the 928 Automatic TT dimensions, I may not need that even.

Vilhuer

Shaft is 25mm on both versions and bores are same size also. Problem isn't them. Clamp bolt location is around 10mm different meaning new bolt groove needs to be cut into early or late TT center shaft when they are used on opposite period gearbox.

Landseer

This is interesting, but am having a little trouble following.

Can you guys summarize the possibilities against these criteria?

Assuming some fabrication is required...

Is there a non-928 5 speed arrangement that might fit in the mid year automatic 928? In the mid year manual?
Can the 928 automatic be made to fit in a 944?

(I have an 83 944 with bad auto trans; also an 84 928 with rough manual trans)