Luis de Prat

About a month ago I went out driving with some other Porsches. On the highway at over 130 mph I put quite a bit of stress on the gears, downshifting to third and flooring it to get maximum acceleration. The 951 is geared so long that even though 3rd seems short, it actually was not.

Drove back home about 60 miles without a problem. Parked the car and the following day I went to get some new rear tires and as I was driving through town slowly I suddenly heard a pop from the back of the car and a constant clicking sound.

At first I thought it might be a CV joint but then I narrowed it down to 3rd gear. My guess was confirmed when I eventually I saw the wreckage...





The car is repaired now, and 3rd gear is as good as it ever was with a new synchro ring and needle bearings, but I wonder what may have caused this. The gears didn't grind when I downshifted. I just put a lot of pressure on the car to accelerate, but would that cause a pinion to break three teeth like mine did?

Mike C.

It's hard to say Luis. It may be that a small crack at the root of one (or more) gear teeth slowly propagated until a high stress event was enough to pop it. It might be interesting to have the gear magnafluxed to see if there are any cracks in the other gear teeth. I could be a defective heat treatment on the gear teeth...

LuisGT3

Ouch,
Was this car in PR? If so, I blame it on the bad roads...

Predator

So-o-o, at 130 mph, you downshifted to accelerate? 130 mph in a 951 tranny equates to over 8000 rpm. Sounds to me that you're damn lucky you didn'y grenade that 4-holer, or lock up the rears and kill yourself! Jeeeze!

bearone

lucky indeed. fools and children.

87951

badcoupe

nice job! Looks like my last trans but all the teeth were gone on several gears!

MTM

I think 130 mph in 3rd gear would be about 9500 rpm!

GOBOGIE

Gotta love the downshift into the 3rd on the turbo S...

Chris_924s

OUCH!! Metal fatigue would have cracked/ split the entire gear, not just a few teeth- imho.

GOBOGIE

Chris, I'm hurt you took my quote out of your signature ;-)

Campeck

yeah. third gear in the NA hits 80 mph. i doubt it hits 130 even on a turbo. you didnt mention if you overrevved it or not.

Rock

maybe he meant he got up to speeds of 130mph, and he had to downshift to third on a different occasion during his 130mph flight

GOBOGIE

Yeah, he wasn't saying he hit 130 in 3rd gear. The turbo S definately isn't gear'd for 130 in 3rd gear ;-)

89magic98

Maybe he meant to type kph?

Campeck

that would make sense huh...although thats not even that much either. what is that..about 85-90 mph?