in the 2002-2004 z06 transmission? Essentially I am asking what my options are. Long story boring, there seems to be a predisposition for the c5 transmissions to grind upon quick shifting at high rpm's. This to me is not normal. I am in the market for an 02-04 z06 and have already driven one that had an extremely pronounced and unacceptable grind shifting quickly from 1rst to 2nd. So much, that I may be turned off to Corvettes for good if this is the norm.

What are my options? I plan on road course racing the car, and shifting at redline fairly often. Any type of grinding to me is unacceptable. Does a vendor make a fully rebuilt transmission with heavy duty parts? Are the synchros the culprit? What's the deal?

I plan on using the MGW short shifter and a shorter derlin ****. I was also planning on running Amsoil in the trans. That being said, I don't want to rely on a simple oil change to solve any grinding issues that may persist.

TIA

 

No,,,,it is NOT the norm. I drive my 02 Z very hard and get lighting fast shifts with out any grinding. She had 50K on the clock now with out issue. I have expierenced that grinding that your expierencing in my 50,000 mile 98 coupe. It would grind just a little in 4th and 5th. So, I changed the stock 50,000 mile dino ATF out for some mobile 1 synthetic (yea,i know about the paper blocker rings)

In my opinion, about 30K miles on tranny fluid and it time to change it.


Changing the fluid Completly solved the issue. So,,,if you find a car that your interested in and it has this issue, ask the owner to up-grade to AMSOIL Tranny ATF. If it fixes it, WELL DONE. If not, move on the the next C5.

My 2 Cents

Bill C

 

I disagree with the statement "seems to be a predisposition for the c5 transmissions to grind upon quick shifting ". Mine has 50k miles and doesn't do this and has never done this. I think the problem you are referring to is pretty rare.

Perhaps it's time to flush/bleed your clutch fluid. Sounds like you either have a clutch not completely disengaging or bad syncro rings or maybe both (clutch issue killed synchros).

 

Thanks for the replies gentlemen. I would assume that there is a way to adjust the clutch pedal on the z06, correct? My research vaguely mentioned something about a self-adjusting clutch, so I am not 100% sure.

 

In stock form there NON ADJUSTABLE. Aftermarket Master Cylinder now has an adjustment. Either it works or it doesnt.

BC

 

I DO agree with the comment that it is a really common problem. Even 10-15% is really common. The cars do have a known issue (and many dealers agree). But then they blow it off, which sucks, but that seems typical. I also agree with the clutch killing synchros point, but that can also be bad shifting habits. I think the more common issue is as described below:

Consider something as simple as the alignment of the shifter rods, which the C4 6 speed did not have (alright, technically they did, but they were in the ZF transmission body, where they were set up by ZF). The alignment-design issues have been constantly improved, but extend even to the C6. Varies greatly from car to car, as you would expect with what is basically a quality control issue, aggravated by arguably a weak initial design. The C6 shifter in the 2009 is, according to some GM papers, much improved, and that is what I am doing. I got mine from Gene Gully, who immediately pointed me to the 2009 shifter (of course, I asked). Gene is one of the best resources this forum has. Can't say enough about the guy. (what is it? gmpartshouse? His link is all over various posts, forgive me for not stopping to look it up now)

So I conclude:

1. If you car does not do it, you have a car that is set up right. Drive on, and enjoy.
2. if your car does do it at some level, the most straight forward approach is to have an expert set it up, but finding one to trust may be hard to do.
So if your car does do it, you can avoid the risks of #2 above with another shifter of your choice and also for any other benefit you want or perceive.

In the meantime, go easy, so you don't damage anything in the meantime (this entire discussion obviously has the fatal flaw of "ignoring" the obvious fact that there are some transmissions out there that really do have synchro or other problems).

There are many good, and well thought out threads on the forum already. Just avoid some us who post absolute conclusions based on our car, which is a statistical sample of.. one.

Please, do what many forget to do. Post your solution so we will learn what you learned.

Regard

PS: Everyone says the MGW is the pick of the litter, and at the opposite end, many also love the C6. And in between , most have been happy with whatever they have done. Which makes a strong argument for my case that it is an alignment issue aggravated by design issues. In other words, almost any fix works.

Hope this helps, please keep in touch.

 

I have only driven a few C-5s and the only issue I could find was the transmission fluid has to be hot to shift properly. My Z does not shift well at all cold and I am very careful with it until it gets to full operating temp. After the temp is up it shifts like mildly notchy butter! I get no grinding. I have changed the fluid twice since getting it with 16,000 miles, it now has 42,000 and I only use Royal Purple which seems to work fine.
Oh, and I suck out the clutch fluid at least twice per month and only use synthetic.
I drive mine everyday, rain, snow and occasional sunshine!

 

I agree with the fact that the shifting improves with temperature increase. My Z doesn't have a grinding issue, but shifts much better when hot. But under no circumstances does it equal my C4 ZR-1 in shift quality. Not by a long, long shot. Furthermore, cold or hot, the shift (i to 2 especially) is dramatically affected by any sideways pressure, or "twisting" I may inadvertently put on the shifter.

No question in my mind that GM did not intend this, and what we have going on here is several issues, and to make it more confusing, the issues have greatly varying degrees of seriousness. There are too many reports (way, way, too many) from posters where going to a new shifter, or adjusting the existing shifter, eliminated the problem. Changing the trans fluid is probably a good idea, but once again, if one fluid (RP) is so good it helps, and the stock fluid (or, by implication, other fluids) have problems, then we have an issue. As to changing the clutch fuid every other week! I would get rid of the car first. There is no way you will convince me that is an acceptable maintenance level.

All of this goes back to my original point that all of us are hanging our hopes on various solutions based on personal experiences with too few cars to be statistically signifigant. But the entire body of posts on the forums, and the repeated reports of improvements, suggests a quality control problem with design and or assembly, and the fixes done by the members (especially replacing the shifters) has the effect of relieving the problem.

It is not acceptable to say, as a stupid dealer told me, the C5 always shifts bad, and that's just the way it is. BS . And over the top maintenance routines to minimize the problem, while helpful, are also unacceptable.

One last point is to keep in mind that this same issue lives on in the C6 to some degree, which I suspect is why GM has worked a lot on the issue, and did the press release about the 2009 (not to mention the popularity of the aftermarket shifters which, relatively speaking , were unheard of in the ZF C4 era).

 

I just changed from stock to the new MGW short shifter just because I wanted to and I like it. I have made some "go faster" mods to my '02 and can't resist hitting the red line when I can. My trans does not grind - clutch releases long b4 it hits the floor but each shift seems stiff or takes too long for me to feel comfortable doing a power shift. The car only has 9600 mi. on it - is this normal or what? The change from stock to MGW made no noticeable difference. I'm a young geezer that grew up with 4 spd Muncies and Hurst Comp + shifters that you could slam after you adjusted the stops. My biggest concern is doing damage to a syncro. Any ideas or comments?

 

You brought up adjustable stops. From my research, the only aftermarket shifter with adjustable stops is the Billet Products short shifter from Australia. I tried to get some more info from c5 members who use it, to no avail. It does not seem to be very popular in the U.S. market.

 

The Hurst shifter definitely has adjustable stops. You are not supposed to need them since the C5 transmissions have internal stops (the stock shifter does not have stops), so a lot of people remove them. I went ahead and adjusted mine where I could slip a piece of paper between the stop and the shifter when pulling back on the shifter.

 

Good to know. I have emailed Billet Products about their shifter. I will keep everyone posted as to what I find out.

 

From the cars I've driven, this is normal. My shifter is stiffer than your average car. Like others have mentioned it does loosen up some when the transmission warms up.

As for grinding, only one thing causes it no matter what anyone says... synchro not working as designed. Maybe due to wear, or possibly a combination of wear and the clutch not completely disengaging. Nothing kills synchros like bad clutch hydraulics or poor shifting technique - basic transmission stuff. Sounds like you don't have this problem.

 

That's the impression that I am under. The synchros are either bad, or they're not. Nothing else (good shifting etiquette in place) should be causing any sort of grinding.

 

It seems there are a lot of clutch/transmission probloms with abused Z06's. If its grinding, then the syncros are more than likely bad and/or the shift forks are bent (drag racing). A z06 in good condition will not grind. It won't be as smooth as an S2000 or miata or bmw, but it sure as hell won't grind.

That seems to be the norm now that the cars are getting a little older, drag race the hell out it and then sell it to someone else when the shift forks are bent and the clutch is slipping.

Keep looking for a car in better shape. My .02

 

Well I feel better now - I'll just shift like the grandpa I am and then red line it! Snow on the roof doesn't mean there's no fire in the furnace!!!

Y'all are great - Thanks

 

My 02 has 55k miles and a B&M Ripper.I did the AV mod ( 2 washers) and changed to RP fluid.

Shifts firm with a solid feel and with a classic "snic-snic" sound to it.I also change the clutch fluid every OC.

\db2
Carolina

 

Can you elaborate on the washer (AV) mod? I am all about the snic-snic bolt action rifle of a good (short) shifter.

 

The KIRBAN Shifter also has adjustable stops and shifts very well. It also has additional centering springs which helps move the shift lever to the 3rd/4th shift gate. This really helps prevent grabbing second gear when shifting from 3rd to 4th.

Everyone who has driven my ZO6 comments on how good the shifter feels.

Bill C

 

I liked the Kirban too, on my C5Z, much better than the MTI six shooter I had on before it, and yes the Kirban had adjustable stops. My tranny guy made me get a shifter with adjustable stops after I rebuilt my tranny due to grinding (broken cheap stamped synchro keys which I replaced with solid billet ones, steel 3-4 shift fork and bronze fork pads.)