Gearboxes stripping teeth from too much torque.

morrisman1, Mar 27, 7:08pm
Gday, I dont have this issue but Im about to buy a gearbox that has been behind a rather powerful engine (starting to get in the 'prone to smashing boxes' range). Would the teeth fatigue over time from extra stress and be more likely to fail with our engine (2L non turbo, 130kw atw) or because it hasn't broken already will it be just fine. Its a spare for the race car so most likely won't be used unless something happens to our current box which I know is mint.
vtecnet, Mar 27, 7:28pm
Interesting question, but my CRX with turbo added didn't break the gearbox with 7 years of abuse, (2x factory TQ and HP), not sure how much but enough for 13.5@104mph on the 1/4 Mile.
The New Owner does this most weekend at the track http://img823.imageshack.us/img823/1070/57921055257319477337746.jpg

Its only a tiny gearbox too, he changed it, as he was worried that it was going to blow, the replaced was in worse condition then the abused one, but I did change the gearbox oil now and then, perhaps his replacement gearbox had never had its oil changed.
peril787b1, Mar 27, 8:04pm
The gearboxes ability to handle the power is not the main issue there, it's more the level of abuse/bad shifting/lack of clutch that it may have had to deal with in the past. What is the vehicle/engine/gearbox!
morrisman1, Mar 27, 8:10pm
I think it came from a pulsar with a SR20VET. Gearbox is a RS5F32V from a VZR pulsar. A primera in the club was trashing these boxes coming out of the hairpin at teretonga, and that was a SR20DET but that was largely driving style and letting it spin up heaps then it would grab and bang goes 3rd gear.
sr2, Mar 27, 9:28pm
In my experience even disassembly and crack testing will only pick up the last 10 to 20% of a gearboxes fatigue life. After many years of trying to keep gearboxes together under racing conditions my motto is replace, replace.
If you are in the lucky position of still being able to use standard internals I would avoid any box that has been in a competition car like the plague.
Rotate (i.e. sell) your box on a regular basis (well before any sign of failure) and replace it with one out of a standard road car. The increase in reliability for the small amount invested, makes the exercise well worth it.
snoopy221, Mar 28, 12:03am
Reality is any box.
IS ETIER SUMNTINK DAT FITS AND FEELS RIGHT

Or,,,,,,,it's an EX.
pollymay, Mar 28, 2:57am
It's torque that does the damage. Also shockloading and flat shifting will destroy it. I normally get a couple seasons of racing from a box but after that it's scrap.

It does depend on what it is though. Subaru comes to mind for shockingly unreliable drivetrains when driven hard.
doug207, Mar 28, 5:39am
Those VZR boxes are nice. But I'd only get it if it's uber cheap after being thrashed.
At least you're not trying to make a Mazda gearbox last.
sr2, Mar 28, 6:40am
We had great reliability from the 6 speed in out Subaru Spec C Type R. Went through a few clutches though, the amount of traction it had was a little unforgiving on the starts.
morrisman1, Mar 28, 5:56pm
sweet, thanks. I hasn't been in the car long, and its a daily commuter not a race car. The guy is after longer legs than the 4.4:1 diff in them gives.