Kevin_k

Yesterday was my second HPDE day of the season. Prior to my first date I had transmission fluid changed in my 02 Z06. The car has about 50K miles and I have had it for four years without a problem. On my fourth session of the day the car got stuck in 4th gear and I could not move the gear shift. I got the car off the track and no matter what I did I could not get the car out of 4th gear. I let it sit for a while and when the car cooled off I could again shift gears without a problem. I took the car out again but this time I was not very hard on it and everything seemed fine. On my session after that I drove the car in my normal style and it did it again. Stuck in fourth, can’t move gear shifter but everything else ok. Again I let the car cool off and again I could shift gears like normal. At this point I decided to call it a day and drove the car home. I had no issues with the transmission on the hour drive home.
So what do you all think the problem is? My friend who has a good bit of experience with cars believes that a poor quality fluid was used when I had the transmission fluid changed and that is the issue. The suggestion is that I change the transmission fluid again but this time use AMSOIL. I believe what I should use is AMSOIL Signature Series Multi-Vehicle Synthetic ATF. However, I am not sure if I should be using ATF fluid in a car with a manual transmission. Anyway I could use some advice.

Thanks!

Ludedude

Yes, ATF is the oil you need for the manual trans. Made no sense to me either but there you have it. Personally I run the Redline D4 ATF and change it once a year but Amsoil or any other synthetic ATF that meets the latest Dexron spec should be fine.

Impulsive goat

Fluid is where I would start, I use amsoil torque drive on recommendation from the forum. Haven't had any problems and I daily drive my c5z harder than most.

Bill Dearborn

Who changed the fluid? Maybe they put gear oil in like we used do with older transmissions.

Bill

6SPEEDZ

Most likely it is the keys on the synchronizer slider. The keys are a stamped steel piece and tend to bend or break causing it to wedge in gear. I have had this happen on my C5Z and my old Z28. C5 it happened at a road course Z28 it happened at a drag strip. Managed to get it out of gear when stopped but would do the same thing once any real power is applied. There are billet upgrade keys or struts to help prevent this from happening. i would also recommend a steel 3-4 shift fork while the trans is apart.

Socko

Exact same thing happened to me last year at Road America on my 3rd day and i got to drive home 70 miles in 4th lol. It jammed up on track but popped out after 2 corners. I let it sit a while in paddock and it felt fine. Went back out for the next session and it hard jammed in 4th.

It was 2 syncro keys. I assume when the first one broke it got dodgy and when the second one broke it was straight stuck.

After driving home 70 miles it did come out of 4th so i could get in my garage, but upon playing with it it got hard stuck in 4th and never came out till disassembled.

Ludedude

Yeah good point, didn't even consider that.

555ss

it is definatly the 3/4 syncro keys both of our c5z's have done it mine on the street hers on track. ditto on the steel fork and while there put in the brass pads. also check the blockers.
The gear box and others have the billet keys in stock. they stick hot then you can move it cold thank god loading/ unloading it would have sucked un able to back up

Z06VENOM

Same thing happened to me 2yrs ago...

Found this on the magnet...


This is what they look like.

Vettechris996

I had the same thing happen to my C5Z. Eventually it will not come out of gear. Talk to Rick at RKT56 is you don't feel comfortable handling opening up the trans yourself. He built my trans and is a great guy to work with.

ratt_finkel

Yup. This.

When I bought my C5Z I drove it 1,800 miles without touching 3rd or 4th. Co-driver accidentally shifted to 4th, and we drove like that for 2 hours before it popped out LOL

Kevin_k

Thanks for all the responses looks like I am going to have to have the transmission rebuilt. It just seams strange that once the car cools down I could drive it without a problem.

Anyway pulling the transmission and rebuilding it is way beyond my abilities so could I get a recommendation where I should take the car to in the Seattle Aria (Acutely Bremerton)

Thanks again!

LateBreak

If it were me, I'd take the opportunity to swap out the Z06 trans for a base model trans with the basic upgrades installed. The Z06 ratios suuuuuck on the track, base model trans has a better 1-3 set and 5-6 are better for highway cruising as well. It's a win-win.

You can generally find a donor trans for about $600, which is probably what you'd spend on parts if the synchro was damaged. Beyond that, you can send it out for the same upgrades without taking your car apart first.

lefrog

It happened to me once at the track before but it did not happen since. Would a trans cooler be able to minimize the issue by keeping the temps lower or it's just a mechanical issue anyway and it will happen no matter what?

555ss

The stamped steel keys are just weak by design and under hard use they fail it only takes one to break and it jams the syncro some times they then fall free and the other 2 will continue to work but if it is pushed hard they fail also. My car broke one on the street it then drove fine but after reading about the issue I pulled the trans and found just what the above picture showed one broken key stuck to the magnet. My gf's car broke 2 on track and it was stuck in gear till it cooled then shifted notchy but when pulled the keys were trash. I have since installed billet keys and part of any race prep of a c5 along with the steel 3/4 fork and the brass pads. With those things done 5 years of HARD use ( i'm also a drag racer and I still power shift the vette) and no issues.

mwestc5

Towards end of my 2nd day alls going well I have my student in my car( he's a Mustang guy but a good guy-but don't hold it against him) coming out of turn 6 through the laces tried to go from 4th to 3rd for the toe and I've got nothing. Shifter won't move anywhere, for a few seconds I had no clue what gear I was in, thought I was in neutral & had nothing. Then realized I was in 4th.

I came off track into paddock trying to shift, double clutching & getting nowhere. Got to my space, shut car off & tried shifting out of 4th & it did. Started it up drove around the outer perimeter road was able to shift through the gears twice third time it stuck in 4th again.

Only way I could get it out of 4th was to shut it off - restart it and keep trying till I got it out of 4th. I let it cool down awhile and drove around the outer perimeter road again, this time it shifted OK. Went back on track & had same problem at same spot again. Did not complete 1 lap but made it off in 4th.

I have a 250 mile drive home, most of it interstate. I figured worst case I would drive home in 4th. I had 2 good days in, my student was signed off to solo in his Mustang, I had no further obligations for the 3rd & last day. My plan was to drive home in 4th gear the following morning.

I made it back to the motel shifting through the gears with no problem. Once at the hotel I searched out my problem--found this thread with my exact problem.

I want to thank everyone who contributed to this. You all made it possible for me to drive the 250 miles home relaxed with piece of mind. I drove home avoiding 4th gear completely. At 1st I had to be very conscientious of not shifting to 4th. After maybe 15 minutes it was perfectly natural to shift from 3rd to 5th.

I even considered going back to the track driving without 4th. I am no mechanic & had no clue if I might cause more damage and jeopardize my ability to drive home.

The drive home was absolutely flawless. Now I can tell the guy who works on my Z exactly what's broken and what to replace the failed parts with.

So, thank you very much to everyone who contributed to this thread
M West

Kevin_k

Had to have the transmishion rebuild. Did as suggested when i had the transmishion rebuiltin. Billet Keys, Steal Forks, Brass bars also replaced clutch and flywheel with one for a c6

dowroa

Is this an issue that is just with the T56 and was this solved with the 2008 TR6060 transmission? Or does it have the same issue?

Thank you!