Using a weak transmission in a powerful car

I haven't posted here in a while so I hope I chose the right subforum!

My buddy and I have a car with an automatic that we want to convert to a manual. It's a Porsche 968.

We're looking for a transmission for a reasonable price. I already have one which will bolt in, however it's from a model that had much less power and is notorious for barely being able to handle its stock power (a 944 n/a).

I was thinking about ways to detune the engine just to get the conversion done and make the car driveable, and we could put in the better transmission very easily later on once we obtain one.

Then I had this thought. The problem is actually the ring & pinion of the 944 transaxle. So if that r&p never sees more torque than it used to from a 944 engine, then it should survive, right? The most torque it is used to seeing is 150 lbft * 3.6 1st gear ratio = 540 lbft, if I am thinking about it correctly. And if the 968 puts out 225 lbft, then using 2nd gear, that becomes 478 lbft.

Ignoring the fact that starting in 2nd gear is a drag (this is meant to be temporary and allow us to get the tough parts of the conversion finished), is my thinking correct that the new r&p would experience less stress than before by not using 1st gear?

I'm on my 4th transmission in 3 years because I've tried to be "cheap".    If you can't afford to do it once, how can you afford to do it twice?

Sticky tires break transmissions.

If you're driving halfway civilized and not sidestepping the clutch, you should be ok until you put the better transmission in.

In reply to ShawnG :

We don't build these cars to drive them "civilized".

The GT40 racers use that transaxle in their mid engines cars.

They put a chro-moly retainer plate on the back and some use a clutch delay to prevent clutch drops (these were on rental cars).

There have been several threads around here on the Audi 016 transaxle.  In or two of them I provided links to make your own retainer among other improvements.

Limiting the movement of the transaxle by stiffening the mount and adding a brace to the chassis helps quite a bit, especially when combined with stronger engine mounts.

I figure if the 944 S transaxle survived being blasted by the 500hp turbo motor in my 951, a reasonable should be ok if you can avoid clutch drops all the time.

Honestly, I'd leave the automatic, they tend to handle torquey motor better than manuals, but that's just me I guess.

There are a few 944s out there that have custom 01E Audi transaxle in them. Or find a 951 trans or suck it up and pay for a 968.

My Opel will likely be running a NA 944 suspension/drivetrain behind a boosted 07K 5cyl. I have been looking at options and have considered looking into a Corvette transaxle from a C5 or newer. I think 1995+ for them. A sweet T56 would give you a decent strength 6 speed if you can adapt it.

3L33ter said:

I haven't posted here in a while so I hope I chose the right subforum!

My buddy and I have a car with an automatic that we want to convert to a manual. It's a Porsche 968.

We're looking for a transmission for a reasonable price. I already have one which will bolt in, however it's from a model that had much less power and is notorious for barely being able to handle its stock power (a 944 n/a).

I was thinking about ways to detune the engine just to get the conversion done and make the car driveable, and we could put in the better transmission very easily later on once we obtain one.

Then I had this thought. The problem is actually the ring & pinion of the 944 transaxle. So if that r&p never sees more torque than it used to from a 944 engine, then it should survive, right? The most torque it is used to seeing is 150 lbft * 3.6 1st gear ratio = 540 lbft, if I am thinking about it correctly. And if the 968 puts out 225 lbft, then using 2nd gear, that becomes 478 lbft.

Ignoring the fact that starting in 2nd gear is a drag (this is meant to be temporary and allow us to get the tough parts of the conversion finished), is my thinking correct that the new r&p would experience less stress than before by not using 1st gear?

I've raced with badly worn weak transmissions and if you're gentle they will last. If you have no mechanical sympathy and insist on slam shifting, flat footing it.  It won't.  

Thanks for all of the input so far guys.

In my personal experience, and from years of reading, the NA transmission is too weak for an NA, and the other 944 variants' transmissions are plenty strong. But I will definitely look into these 016 reinforcements mentioned!

Our intention is to get a 944 S/S2/turbo trans though. 968 transaxles are too expensive for our car and what we want to do with it. C6 Corvette transaxles cost too much and a FWD 01E has to be sourced from Europe IIRC, and both options don't make sense since a 951 trans is cheaper and bolt-in and satisfies our needs, once we get around to finding one.

This car definitely won't be raced or driven hard with the temporary transmission. And even after the better one is put in, just occasional track days with 2 good drivers.

My main question is if a weak r&p will actually be spared abuse by skipping 1st gear. It makes sense to me but I could be thinking about it all wrong.

3L33ter said:

My main question is if a weak r&p will actually be spared abuse by skipping 1st gear. It makes sense to me but I could be thinking about it all wrong.

That idea has merit in my opinion.

The chro-moly bearing retainer plate helps save the R&P among other things.

Using a limited slip will help prevent wheel spin and that will help the differential not spit parts out of it.

If the GT-40 and Lambo replica folks can beat on them behind their V8's and V12's, you should be fine.

A buddy runs a 924 Turbo with the Porsche-based transaxle in ChampCar, etc. and they start from the pits in 2nd and they don't have a lot of issues with failures due to that.  The 924 Turbo transaxle is actually the strongest available, but it has its own torque tube and they are pretty rare along with their internal parts :/

Second gear starts will reduce the R&P load exactly as you expect. The clutch, on the other hand, will have the right to protest!

You could always mount tires that don't have a lot of grip.  That way the tires break loose before the diff breaks.   LOL  

In reply to Purple Frog (Forum Supporter) :

That was my thought too.

Here is a thread on the 01E into a 944:

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/1025568-944-01e-swap.html