I have been lurking around these formums for some time and I appreciate the body of knowledge and experience. Now I am brave enough to ask for some direct feedback and comments.
We have had a catastophic failure of 3rd gear in the 915 gearbox in our racecar.
The car:
74 911 Carrera track only
Motor:
3.2L high compression, high lift cams, weber carbs.
HP? not dyno'd but likely high 200's - low 300's? (per DYNO2000 simulation)
Gearbox:
915 stock box with 7/31, facotry LSD, new syncros, dogs, later mainshaft, later 4th and 5th gears to bring ratios closer. 3rd gear is stock. Swepco fluid.
The issue:
The third gear has been rounded off on the main shaft - the Pinion shaft part of this gear is just half ground off.
Situation:
Under load in 3rd gear just before shifting to 4th on main straight at Mosport.
Totally by surpise - to warning - no noises.
Something let go - engine reved to limiter - and no drive.
At the same time - the clutch let go. basically the inner part rotated right over past the springs and poped the springs out and snaped the 4 rivetted posts.
Here are pics of clutch and gearbox.
Any theories, thoughts? comments?
Is this common issue with 3rd gear?
