TeufelHei

I am looking seriously at a recently rebuilt '84 transmission and was wondering at the possibility of swapping the 2.72 gears from my '81 in to replace the 2.36s that are in there. The '84 is has a LSD, any additional issues there?

jyoon

i thought the 84 came standard with the 2.72? you have to measure the backlash on the ring and pinion and also the tolerance on the 5th gear. you also need a 5 ton press to get the gears off. sorry if you already read this stuff in the manual. i did a rebuild not long ago.

m21sniper

The 84 is 2.20:1 i believe.

jyoon

doh, i think i'm thinking euro.

m21sniper

I wish mine was 2.72:1, lol.

Wait...i wish mine was 3.73:1...

Someone needs to get into the custom 928 ring and pinion business. These cars cry out for some serious US appropriate gear ratios.

jebdog

The pinion shaft is the main shaft of the 5 speed and any change is a complete disassembly and rebuild of the transmission in addition the ratio of the lay shaft gears is different on transmissions so first through fourth would effectively be even lower than a euro transmission if you just change the final drive gearing. Many years ago a custom 3.09 gear was made cost about $3,000 very few people have ever seen one.

Ron_H

For a long time, I lusted for a 2.72 but then this put to rest my desire to lose my 2.2:

John Veninger

Tim,

As mentioned, it's an entire disassembly of the trans to do the swap.
Might just be better to find what you need complete.
FYI-I'll do the leakdown and compression test this weekend on the hybrid.

Vlocity

I've never done the math....but what is the top end with the 2.72 gear. Saying 6000 RPM and 6250 RPM.

Regards,

Ken

jyoon

if you just want the lsd, i think you can just swap the ring gear. if you put in the 2.72, it may be too low. i kind of think my 2.72 euro gearbox is a little low. 3rd gear tops out around 90 iirc.

m21sniper

LOL, 2d gear in my US A/T with 2.20s tops out at 98mph.

I think i could use 2.72s.

TeufelHei

Alright so, it's a little more complicated than your average car's transmission. Oh well, I thought I might be able to pull something off.

AFAIK all the three speeds were 2.72 geared. Mine is a five speed though.

John...thanks, sorry I've been out of touch. I'm looking forward to seeing those numbers!

Scott M.

IIRC, about 5-6 years ago (in an issue of Pano), someone had the 3.09's made by a place in Canada.

I have the 3.09's in my GTS. Top speed 5th gear with the stroker is around 140ish. Not very good track gearing. 2.75's would be better.

Scott

TeufelHei

So basically what I'm getting here is that there is no easy way to gear up the 928 transaxle? Where can I find a list of transmission gear ratios for each gear? Not the final drives mind you, but the individual gears. I imagine it's in the manuals somewhere, I'll start looking.

TeufelHei

Wheels of stock dimensions with 2.72 final drive ratio and a 1.00:1 5th gear gives you:

163 MPH @ 6000 RPM
177 MPH @ 6500 RPM
191 MPH @ 7000 RPM
204 MPH @ 7500 RPM

This is of course with drag notwithstanding. This is also why it is amazing that the White car went as fast as it did. Anyone else out there breaking 200 MPH?