Hey fellas!

I have an '04 Z that is bone stock with 34k miles.

It grinds on the 2-3 shift just about every time at WOT, otherwise shifts completely normally when driving normally.

I've completely flushed the clutch system with DOT 4 and Ranger it pretty often...it used to dead-pedal and grind at WOT but now it only grinds, the pedal is being pushed to the floor and it's stiff.

I also took the clutch access cover off and I've got plenty of meat left on the stock clutch, the slave doesn't appear to be leaking either.

SO...do I have a clutch problem or a tranny problem? I've also got a weird vibration at about 3k, plugs and wires have been ruled out (both new GM stuff). It almost feels like the flywheel is out of balance...but it appears to be OEM.

This has turned into a head scratcher for me...

 

Sounds like it's grinding when you shift aggressively. I started with a 3-4 grind; then developed a 5-6 grind, and finally got completely fed up when I got my 1-2 grind.

The problem was with my trans. I had it rebuilt at around 70k to handle more HP than I will ever make on my car. The guy who rebuild it said my synchros were ALL kinds of torn up (along with my reverse gear for some reason...).

Trans problems are more common than you would think on these cars. There are an awful lot of plastic parts in our transmissions for cars that make so much power in stock form.

 

At 34k miles? This blows my mind...

 

Have you verified your shifter is correctly aligned? If not you need to check. It could also the that the shifter housing is loose. As I recall there are some rubber washers for the mounting that may need to be replaced.

 

WELL,,,,,,,,,,,, You sucked out and renewed the clutch fluid but,, have you actually BLED the slave? That would be the first thing that I would do. You must make sure that you don’t have any AIR in the system

It’s a PITA but,, until you get ALLof the old fluid out of the slave and make SURE that there isn’t any air in the clutch hydraulics, you cannot rule that out. If there is any air in the system, it will affect clutch disengagement.

As I was reading your description of the problem, I was shouting to myself "CLUTCH DISENGAGEMENT ISSUE"

The only way to rule that out is actually BLEEDING the system.

Part TWO: “Transmission fluid”. I changed out my 02 ZO6 MN12 fluid at 27,000 miles and was very surprised at how contaminated the ATF was. Everyone said it was normal but at that low mileage, IMHO, it should have been clean. I replaced it with Synthetic ATF and the transmission shift quality improved a LOT!

Obtain some AMSOIL Torque Drive ATF and switch out your trans fluid.
Forum member SUBDRIVER is the man to contact for all the facts on that product. IT WORKS EXCELLENT!

If you have a clutch disengagement issue causing or contributing to the grinding issue, the longer it continues, the more your synchros will suffer. It will start out as one gear and manifest itself to 2 gears then 3 and then other shifting issues will happen.

Hope this helps.

Bill

 

Theres a known problem with Zs and shifter misalignment. Do a search for AntiVenom shifter fix. As stated above its about replacing washers with copper washers. Also the vibration could be torque tube bushings on its way out with alot of cracks in them.

 

Yes, flushed as in removed the exhaust, tunnel plate and accessed the bleeder screw and bled it.

Tranny has said fluid in it, swapped in at 32k.

 

These responses, I like them

I don't think it's the torque tube bushings...the vibration happens with the car sitting still and the clutch pushed in, not spinning the shaft or transmission.

 

If you have a ZO6, you do not have the rubber bushings between the top torque bolts bolts and the torque tube. You have two steel spacers.

 

The shaft is connected to the engine. As long as the engine is running, the shaft is rotating.

 

Isn't the clutch between the engine and the shaft? If I have my clutch pedal depressed, the shaft is not turning...correct?

 

Unless I am out of my mind, the transmission is rear mounted, so the clutch, pressure plate, and flywheel is in the rear after the prop shaft. The shaft is always turning on these cars.

 

Negative, the clutch is mounted to the back of the engine...at least mine is, I know this for sure

If you have an auto car the torque converter is probably right in front of the tranny and mounted in the rear as you say it is...

 

Ya, I just looked it up. I thought the setup was simmilar to the autos!!! Nevermind brother!

 

Lol, I guess your out of your mind. The trans is in the rear the bellhousing is up front...

 

Yessir! I clearly was mistaken!

 

Actually i was mistaken too, the antivenom fix is for notchy shifting. There is however a alignment procedure out there that should be done as a first attempt to remedy your situation.

If that doesnt fix it, then its your syncros worn down and needs replacement. The syncros help shift the trans at high rpm only. I had the exact same issue with mine. But instead of just replacing them, I had ECS rebuild the whole trans to racing specs so I dont have to worry about it ever again.

 

Either your shifter isn't aligned, your*clutch isn't disengaging or you have a trans issue.*

I would start with the easy stuff first and work my way to pulling the trans.*

Align the shifter: See below

Check the area around your master cylinder for fluid leaks

Check around your slave cylinder for leaks.*

Replace your trans fluid (use a good quality synthetic) - Looks like you've already done this

Bleed your clutch fluid from the slave. -*Looks like you've already done this

Pull the trans and have your effed-up internals replaced.*



Shifter Alignment -*You could easily find a detailed writeup with pictures if you search this forum but... from memory:

Ebrake on

Trans in Neutral

Remove your center console

Remove the rubber shifter isolation boot

Loosen the three torx screws

Put the alignment pin from your stock shifter (you can use the appropriate size drill bit or allen key if you don't have the alignment pin anymore) into the hole at the front of the shifter.

Torque the torx bolts down to spec (I think it's 22 ft lbs) while the alignment pin is in place.

Remove the alignment pin and put your car back together

 

It is possible to have a failed slave cylinder that bleeds properly and does not show any fluid leaks under the car. My last one that failed was SLOPPY loose on the barrel of the unit. It would barely disengage the clutch, even at idle. I could move the TOB side to side 1/8" or so, yet somehow did not leak fluid.

I am not sure about your driving habits, but I'm on my third slave in the 50k miles I've put on the car. The original slave lasted the original owner for the first 50k, so clearly aggressive driving will kill these sooner. I would not be surprised at all if yours is failing at 30k miles.

Jack

 

If you grind in 3rd only at high RPM, it's most likley in the transmission. If the shifter alignment was off, you would have issues in other gears as well (not always but a good rule of thumb).