UKenGB

Hopefully someone can help answer some questions that have come to mind.

The automatics have a large diameter torque converter on the front end of the gearbox, for which the shell (floorpan) has to be suitably shaped, but I guess it's under the rear seats so not noticeable. However, the manuals do not have that 'bulge' in the transmission. So…

Is the floorpan actually the same for autos and manuals, or are the manuals 'flatter' there as they don't have to accommodate the torque converter?

I know there have been conversions from auto to manual, but that would obviously work as the manual box is smaller there. However is it possible to convert from manual to auto, or is the manual floorpan shaped differently and with insufficient clearance for the auto's torque converter?

To be clear, I'm not thinking of performing such a conversion, just trying to get my head around the variations and how they might affect other issues.

Also, later autos have a larger diameter torque converter. Is the later transmission case also larger diameter or were they able to cram the larger torque converter into the same sized case and if a larger case was used, did the floorpan have to be changed in order to accommodate the larger transmission case/housing when they switched to the larger torque converter?

Basically, with all the different transmissions used in the 928, was that area of the floorpan (where a torque converter would be) different to accommodate the different transmissions, or were they all the same shape and so any of the transmissions could be used in any shell?

Also, I note there were 3 diff/final drives with ratios 2.2, 2.538 and 2.75. But are they interchangeable?

Specifically, is the mounting interface between the front of the diff and the rear of the main transmission case the same for all versions of transmission? So for any actual transmission, could the diff be swapped to one of the others?

Anyone know such details?

Darklands

That's the final Drive of a Manual Transmission. You must Change the Center shaft in the gearbox

Shirah

Funny that I was thinking something similar; is the rear hump higher when there is the rear A/C.
Now I'm thinking is the rear hump really really higher for an automatic with rear A/C.
Now see what you've done?

gazfish

I was told by a specialist that my S2 has a larger torque converter space in the chassis in preparation for the S4 transmission as it was built during the transition year.

davek9

TQ space was also increased for the S3 (US 5.0 32v) 85 to 86.5 same as an S4

UKenGB

As I understand it, the original 4 speed auto used the same size torque converter as the outgoing 3 speed, but then later the 4 speed torque converter size was increased. Did any of that require a change to the floor pan to accommodate the larger torque converter and do the manuals of the same year have the same floorpan, with that space just being 'spare'?

Still wondering if the diffs are interchangeable…

Landseer

I dont know the answer. But have successfully installed 89 auto in 84 auto shell. Not sure. But pretty likely there was not a different manual shell. Outer case housing the TC is about an inch larger in diameter. Tight but worked. There are some minor adaptations such as need to utilize that later cabling, both the shift cable and bowden cable. The 89 happened to have a better gear ratio. I thought 2.52. Nicer. Made 16v car much more responsive at normal speed range.

Rob Edwards

For whatever it's worth, there's a column in the PET database for each car that lists a 6-digit body type number- I honestly don't know what it refers to, always assumed it was the code for a particular body-in-white. Obviously the 927s are right hand drive chassis. Not sure about the other differences, may be side marker holes or different floor pans for 5-speed vs auto, but In any case, here's the association between body number and the year and model range for each number: