Mar 20, 2011
So during high rpm shifts(3500+) I'm getting grinding shifting into 4th. Not all the time I'd say about 80% of shifts. It happens the odd time at lower rpms once in a while. Changing the fluid didn't do anything so don't say change the fluid lol. Opinions? the car only has 117000km on it.

I'm thinking synchro's, but don't really want to believe it.
Cyncros for sure , very common with both the C5 & C6 .

I do have a spare trans in stock that has been rebuilt .
the shift forks are also weak in these transmissions. They were aluminum and if you tried an enthusiastic shift, its possible you bent it. This would prevent the tranny from meshing properly. The rebuild kits they offer for these trannys are reasonable but if you're not mechanically inclined then you're looking at around $3k to remove and replace and rebuild the unit you have. You should however at least machine the flywheel, install new bolts and replace the clutch while you're at it AND add a bleeder for the system if your car is not equipped with one. By the time I was done with mine, I think it was around $4k but with the new synchros and steel shift forks I'd say you're good for at least 550hp. In fact with the exception of the output shaft, after you've upgraded the synchros and shift forks, you're pretty much running a viper tranny with the exception of different gear ratios. I would also recommend new gears though and upgrade to the C5 Z06 ratios which are much closer and have only one real overdrive gear rather than the ones you're running.

Just my $0.02
ALUMINUM forks???? Was someone trying to re-invent the transmission. With the Muncie, GM had a transmission that you could work hard for 200K miles behind a 425 hp 427 and still be working fine. Copy a similar design into the six speed and you would have something to last. Don't fix what isn't broken.
Last edited:
For that kind of money you could drop in a nice V6 with a powergilde. That would wake it up.:Biggrin:

I really hope you can get this sorted out, that is big money that probably none of us can really afford. Good luck.:thumbs:
Old Thread: Hello . There have been no replies in this thread for 100 days.
Content in this thread may no longer be relevant.
Perhaps it would be better to start a new thread instead.

Similar threads

Users who are viewing this thread