Are there lower final drive ratios available for a 901 trans?... Yes, I said lower.
Mark D.

... only one I ever heard about is a 7/34 ratio and I think hard to find...stock is 7/31. murray

K, thanks. I'm in the planning stages of a high reving engine, and I'm running into gearing problems.
Mark D.

You have my attention...
914/6GT made peak power (~220) at 8000 and used the 7:31 ratio.
You're looking to spin something faster than that?

Well - 'For Sporting Purposes' references a 6:32 (5.333:1) R&P "for hillclimb cars only." I've heard of these before but don't recall seeing one 'in the wild.'

I've never heard of a 7:34...

I don't see a part number for a 6:32 in the ETKA but as they were never fitted to production cars this is not surprising - Porsche Motorsports only probably. If anyone has seen one of these live it'd probably be the gang at CarQuip in Colorado or Otto's.

The 905 flavors ran an even taller R&P at 7:27 due to the torque multiplication effect of the torque convertor. So you can go taller with production parts but shorter is hard. (Still not sure what you're turning faster than 8000 rpm but have fun with it !)

Check with Carquip in Colorado.
He is frequently on Ebay.

His site has alot of good gear charts and gear information.
Given what Mendeola makes, I suspect you can get what you want if you shop from one of them.
Call Carquip after you read his site...he has tons of gears.
The other guy to ask is Otto's Venice (GIYF)

Rich

... is there an echo in here ? ;-)

apparently there is an Echo in here.

Rich

There was 3 R/P in the 901 type 7:31, 8:31, and 7:27.
I got this info here

http://www.roadglue.com/wiki/index.php?tit...01_transmission

I thought I had heard of the 8:31 but the problem for this discussion is that it's even taller than the 7:31, not shorter per the original question. And - although there's a passing reference in that article - it too shows no application, so we don't know where it was used and there is no part number.

ETKA shows 901.302.902.00 as a 6:29 r&p so there's another flavor heard from... It shows a 912 application but at 4.833:1 is a bit shorter even than the ubiquitous 7:31

So the 8:31, like the 6:32 may be a Motorsports item. Another place to check for early (vintage...) race parts would be Steve Weiner's shop in Portland. (Rennwerk? I should know this but it is eluding me tonight...)**
______________
**finally came to me - Rennsport Systems...

a 912-issue 6:29 might show up someplace like PartsHeaven. My recollection is that all the 6-tooth pinions were a bit on the fragile side but I don't know the intended application here...

How about smaller wheels?

Wow. More input than I usually get on the tech questions. Thanks guys! I've been doing research and planning all day, and I think I have a plan now.
ArtechnikA, to answer your question, it's a T4. I'm planning my next engine to actually fit into a solo class, instead of just building whatever and seeing where I land. What I was trying to avoid was a rather ridiculous weight penalty formula based on displacement, and make up the HP difference with RPM. I think it's doable, and I'd love to be the one to do it, but given where I'm going with the car I've decided to stick with the slower turning 'stroker'. For autocross right now, I can either eat the weight penalty or reclass to XP, but the ultimate goal of that engine is to take me into GT-3 road racing. When the budget allows, the larger engine will be legal for that class as well. It's still no tractor with an 8500 RPM redline, but I can make the gearing work for that.
Crunched a lot of numbers and read a lot of rules today and I've got a solid idea of what I'm doing now. Thanks guys. I'm saving this thread for reference.
Mark D.

8:31 is a 915 R&P
The sporto diff is smaller than that fitted in our boxes and is not useful.

The only short R&P I've ever heard of being used in a 910/914 box is 6:29. I used to have one but let it go fairly cheap a few years ago.
Its approximately 10% shorter than the stock 7:31.