GS-Zero

I've got an '07 C6 Z51. Prior to the past eight or so months, I was able to 1-2 shift flawlessly and in a fraction of a second. Then it started to grind on me at high revs, and then even at low revs depending on the occasion.

I installed:

MGW Short throw shifter (thought that maybe the stock shifter was getting caught, or that my leg had become faster than my arm). This improves shifter feel and reduces throw drastically, and feels much better all around, but did not solve the problem.

Tick adjustable clutch master cylinder (thought that maybe the clutch wasn't fully disengaging, hence the 1-2 grind. The clutch feels more solid now and engages smoother, tighter and quicker, but this also did not solve the problem.

2nd gear is usable, but you have to clutch down, wait a few seconds with the pedal on the floor and slowly, carefully ease it into the gate. I hate to say this, but I suppose that having tried all else, it must be the 1-2 synchro.

Do I really have to spend absurd money to get this resolved? I'm told I should expect to spend thousands and thousands of dollars. Isn't there someone who deals with this sort of thing on a regular basis who can replace the synchro for a reasonable price?

Also, is there such thing as upgraded synchros? Evidently the stock one doesn't take abuse.

Apart from a GS conversion, exhaust and the aforementioned parts, the car is completely stock.

cranky

check with rpm transmission. a forum vendor. very knowledgeable folks. most likely is the syncro blocker rings. probably from the clutch not disengaging earlier. a clean clutch release makes the syncro live a LOT longer. talk to tj at rpm. cranky

Ahmer

Update? What happened? I have this problem now as well.

TripleBlack99

me three

windyC6

Not sure if this method of checking for a worn syncro is still valid......but without pushing in your clutch, gently try to put it in gear. If the syncro is good, it won't go in and you'll notice a very slight drop in RPM (very slight). If the syncro is bad you'll know it cause it won't stop it from going into gear. In other words, you'll hear that gosh awful sound of grinding gears. That's why its important to do it gently.

hisvett

My '12 GS (same trans as your Z51) has always shifted "Notchey" going into 2nd, especially the first couple of shifts after starting out in the morning.

I spoke to someone who is well connected with GM engineering and was told that 2nd gear synchros are slightly different and are of lower quality than the rest of the gears and are not interchangeable. He did mention that switching them out with a popular aftermarket brand (sorry I don't remember the brand name) would solve the issue.

I also remember seeing a thread on CF forum a vendor in the south (maybe Georgia) that advertised rebuilding C6 trans for about $2K and promised that they would shift like butter.

Good luck

GS-Zero

Thanks so much for your help, but I solved this problem almost 3 years ago. You are correct, it was the 1-2 synchro, and I had to have the transmission rebuilt. I had it done by TKO Performance on Long Island. An advisory for those of you who need to have this done, if you are taking down the transmission you might feel inclined to switch to solid transmission mounts rather than the stock rubber-padded ones (there are some made by Pfadt, etc). DO NOT DO THIS. It will amplify transmission noise x100, it is completely unbearable. I bought the Pfadt mounts and took them out right away when I found out they were the source of the noise.

child_of_fire

i have the broken syncho issue now in my 09 z51. still under warranty with only 13k miles...

GM REFUSES to fix this.....Blames the MGW shifter as modifying the car!!! Complete BS...so im looking at 4 g's for a rebuild from RPM.

Racer86

FYI, these are constant mesh gears, the grinding you hear is the teeth on the synchro

GS-Zero

I had the same experience. When I first tried to have it fixed, my car was still under warranty, but GM wanted nothing to do with it. I brought my car to TWO different dealers and both said "they couldn't reproduce the problem, thus they can't fix what they can't see". I won't say which dealer the first one was, but at this particular dealer I have a friend who does subcontract work there, and he said that for the few days the car was there they didn't even drive it. Kept it a few days, let it sit, then called me to tell me they can't find any problems. Moral of the story, your warranty means nothing.

SUB VETTE

BOTTOM LINE: If they can blame it on an aftermarket part they will