V2Rocket

once i get my supercharger stuff all set up/vortec v8 swap (still havent decided, still broke lol) im going to see what it takes to break a 944 tranny.

dont worry, i have 2 spares, one from an NA and one from a turbo (with a cooler )

ive done all kinds of dragstrip type launches and stuff and it hasnt gone wrong yet...i get hopeful every time guys like 944LT1 chime in, he (still?) uses his NA tranny with his >350HP LT1 and launches it all the time and has been fine.

ill take measurements of power every so often with my current (original) tranny and then launch it hard, and see what it takes to break

LT1 theorized that maybe the reason the trannies break is because of the narrow torque band on the 4-cylinders that suddenly loads and shocks the R/P. the v8 has a much wider band that builds up over the rev range. with the roots type the torque band should get wider, rather than a shock at ~5000 it will start lower while the blower is in peak efficiency.

well see what happens

FRporscheman

The SFR sc kit is nice but like I said before the price is unreasonable. Why would anyone take a $2500 car and buy a $5500 kit for it? With that $8k you can buy a 951 and have more power and potential, nicer body, suspension, etc.

tifosiman

My opinion is that it has nothing to do with the torque band.

As the mileage piles up on an N/A trans, the r&p gears wear and the tolerance increases. Ideally the trans would be cracked open at regular intervals and the tolerance shimmed up (although this appears nowhere in the FSM's as far as I can tell). However we all know that no one ever does this. The problem is also exaggerated by the fact that often times people drive around with the rubber clutch in fail mode, which really wreaks havoc on the trans bearings which also adds to the problem. So when you have a r&p that is out of tolerance, coupled with the smaller tooth size of the N/A r&p gears, and bearing issues..........you have a recipe for disaster.

Sure some people like LT1 will claim (and rightly so) that they have had no problems increasing the load on the stock N/A trans. But this should be considered the very rare exception to the norm. An anomoly. This is more than offset by the people that have normal, non-boosted, non-swapped N/A's that have blown several transmissions up during the lifetime of their cars.

The smaller tooth size on the N/A r&p makes it weaker even if it didn't have any tolerance/wear issues.

V2Rocket

maybe mine just works because its only about 80000 miles old. it had about 66000 when i bought it on the rubber clutch but the clutch was fine but i replaced it anyway.

tifosiman

At 85,000 miles my car is on its 5th transaxle.

V2Rocket

but what kinds of mods have you done to yours? your turbo might just be too much

tifosiman

My car is completely bone stock with no mods whatso-ever. I think these cars are perfect as they come from the factory, I wouldn't change a nut or bolt.

V2Rocket

...unless they be on the foglights...or mirrors...

FRporscheman

.... you might own a 944 NA if you own a spare tranny for when that day comes...

944-LT1

I had to come up with a theory for the fact that the guys with the V8's have not blown a tranny. Otherwise I cant explain it and how can we function without theories?!?! When things dont break, we get bored and need something to argue about. hahaha

We have had a snapped CV though. Its crazy because alot of us run wider tires out back which should snap tranny's like twigs with this power but nadda.....well atleast not yet anyways. I guess the best way to tell how strong they are is to rev the V8 to the max about ~425 flywheel horsepower and completely dump the clutch....or let a 16 year old kid drive it after playing Xbox for a few hours while listening to the Top Gun soundtrack.

But Tifo is right. The transaxles are to be shimmed every so many miles to make up for wear. This is more than likely the reason that the trannys fail. But doesnt explain why with more power they dont fail at a faster rate. Thus the theory of shock load of short torque bands.

FRporscheman

Maybe it's the harmonic vibration of the 2.5L 4-cylinder engine that causes wear and failure, while a 90-degree V8 which has no harmonics causes no such wear. Just a theory anyway!

Let's take a 944, add the S2 harmonic balancer and the 968 DMF, and see if the tranny doesn't blow up!

M758

And my 944 has been racing on the same transaxle for 8 years. It did start its racing life as a 47k mile unit and has seen very very few hard starts. Of course it has seen lots and lots of full throttle over 5000 RPM duty with sticky tires, but in 2400-2500lbs body.

tifosiman

I'm certain that autocrossing helped out with my body count. Autocrossing is very dynamic with a lot of load changes.

bbourdon

So... who makes an aftermarket T3/4 turbo exhaust manifold for the 2.5L?

Can you stack head gaskets and get longer head studs for the 2.5? Get the compression down and up the boost!

V2Rocket

i dont think stacking gaskets would be a good idea...lol

you should be able to find a thicker gasket though..cometic?