95 6-speed. I've just started hearing some weird noises from my transmission. A kind of a rumble and a wierd, grinding but chirping noise, sort of like what you'd expect from a large zip tie. The noises seem to happen when it's in neutral or when I'm shifting and in between gears. It doesn't grind when I put it into gear, and it doesn't seem to have any problems or make noise when I'm in gear. Only in neutral or shifting.

First, is that enough info to make any sort of reasonable guess as to what the issue might be?

Second, while looking for info and prices on repairs, I found this:

http://cgi.ebay.com/ebaymotors/89-96...spagenameZWDVW

Is that reasonable or does it set off alarm bells with anyone else? Also, it says it's an L98 but says it's for '89 to '96. Is that correct?

 

That's about what GM was selling them for a yr ago when they dumped their stock. That zf should be a direct fit for your yr C4.

The noises, well you are sure you don't get the "zip tie" noise as you go from one gear to the next? Does the zip tie noise happen if you are in a gear and put the clutch in?

Oh, most important. Go to zfdoc.com and look over the Q & A section. Most all the issues are covered there. Bill is a great stand up guy and will help with advice...just e-mail him.

The noise in neutral could be the pilot bushing, I doubt that GM was still using pilot needle bearings by your yr....but check with Bill about that. Also the zf makes a bit of noise from straight cut gear rattle, ya hear it in neutral & in gear ( 1,2,3 &4). How have you been with the fluid changes? Every 15K is about the norm...usually if it goes much beyond that the older the fluid the more noise ya hear...JMO

Throw out(release) bearing will make noise as you depress clutch and you can waver the noise by going up & down on the pedal.

How is your clutch hydraulic system? No leaks, fluid is GM stuff? You could need to do a r&r on the master and slave....they don't last long with respect to the 100K intervals on the clutch & P/Plate & fly wheel.

My first impression is the clutch hydraulic system and / or the age of the trans fluid....as simple stuff. Maybe the T/O bearing is a bit rusty from age or just giving up. I lean more to checking the hydraulics...Bill says most of the trouble with the zf is caused by failed hydraulics not being caught soon enough. The zf doesn't like the abuse that can happen from failed hydraulics....that is the root cause of most of his rebuilds. The zf don't tolerate bad hydraulics well at all....did I say that before? Not trying to be a wise guy but the hydraulics su$k in Bill's opinion.

Just as an aside you should be aware of the issues with the GM & aftermarket slaves. See that also at zfdoc.com, it's important. Oh GM says late april 07 for replacement slaves under the new Q/C standards.


Tom

 

Thanks for the info.

OK, lots of background. My slave cylinder went out last summer. I had it replaced at a local shop and when I drove it out of the shop I noticed the clutch was slipping. That immediately made me suspicious but everything I read and everyone I talked to (including some threads on here) convinced me that there was nothing the shop could have done when replacing the hydraulics to cause the clutch to slip - it had to be a coincidence. I took it to the local Chevy dealer and the clutch was indeed worn out. I bought the car with 70k on it and it had about 80k at that point. I ordered a stage 3 clutch and aluminum single-mass flywheel and had the dealer install that.

I got the expected gear rattle from the single-mass fly wheel. I also had a leak in my hydraulic system. It was a slow leak. I drove it for about two weeks before the clutch started feeling different. I checked the fluid and the reservoir was almost empty. I refilled it but was unable to find where the fluid leak was. Since I'd just replaced the slave, I bought a new slave cylinder and replaced it myself. No change. I drove the car for a few weeks while topping off the reservoir every few days trying to find the leak, then just bought a new master cylinder and installed it. The leak seemed to stop. I drove the car for about a month with no apparent leakage.

About this time, my job sent me to Bahrain for awhile. The car sat for about three months while I was working overseas. When I came back, I checked the reservoir and it was nearly empty. I refilled it and I've been driving the car for about two months with no apparent leakage.

Now, the tranny has started making the weird noises. And yes, the zip tie noise does occur when I'm changing gears or going from neutral to gear. I'm familiar with the gear clatter noise from the single mass flywheel. The rumbling noise sounds similar to that but not quite the same and much louder.


I've put about 20k on the car and have not changed the tranny fluid since I bought it. I didn't realize it was required that often. I also didn't always use the GM fluid when I was constantly topping off my reservoir.

So, my current plan is to drain and refill the hydraulics with GM fluid and change the tranny fluid, then see what happens. Is there anything else I should do? If I do that and the noise doesn't go away, is there anything else I should try before putting her in the shop?

 

Okay, I can't comment intelligently on the aftermarket clutch set up because I don't know anything about that stuff.

The zip tie noise you hear are the dog teeth on the syncronizers not meshing properly due to reduced hydraulic system effectiveness....in plain speak the clutch hydraulics are toast. What is happening is the system is loosing pressure and letting the P/plate spring back to the "hold" position, so it's like almost not using the clutch when you shift. Another coupla Q's just to pin down my guess on what's up. If you are in gear and step on the clutch do you hear the noise? Can you do the reverse test over at zfdoc.com? Can you get in a cold car and go from any forward gear to reverse easily, no hang ups or balking from the shifter? If yes to the first Q & no to the second Q then you have to fix the hydraulic system, that's the cause of the zip tie noise.

The fluids, well Bill Boudreau says that the GM stuff is DOT3 with friction modifyers in it so it isn't exactly like DOT3 brake fluid...some guys have had sucess using Valvoline synpower brake fluid. Me I just buy the GM stuff, P/N 12345478(?). Check out Bill's test on trans fluid wear vs milage results and you tell me what you would do after reading his results. I do mine every year or 10K miles, but I'm OCD

The missing fluid is in the carpet backing up under the rod that actuates the clutch M/C...that is where it went & you couldn't find the puddle. Ya gotta take down the dash carpet panel and look up to the hole the rod comes thru and you might see fluid on the rod end but it went into the carpet up there. GM used TRW to make the M/C's and slaves. TRW had Q/C issues so most of the stuff made in the last 3 - 4 yrs is deffictive, slave piston seal installed backwards, slave bore run out, bore finish & porosity issues, bad welds @ the line bungs. The M/C's had seals leak and all the slave bore problems and leaks @ the bungs and mal-formed reserviors that leaked. At present there are no replacements in GM's system from the corrected production run...ETA is late april 07.

Take some time & read up at zfdoc.com....it's worth it. I went thru three sets of M/C's & slaves before I finally "built" my own slave that works....but I'm still having issues with M/C's, bore issues mostly as they leak out the back where the rod is. I have yet to buy a M/C that has a good finish on the bore, both run out and scoring seem to be the order of the day with the old stuff. GM never actually admitted that there was anything wrong but they callled TRW out on the issue and the dealers have no stock as of yet...as far as I know.

Sorry to be so long on this and repeating myself about zfdoc.com but it's important. Oh yea, sorry to be the bearer of all this bad news too!

Tom
Oh yea, forgot this part. You need to locate a good slave and M/C and replace the stuff that's in the car. You can send your slave to Bill and he will put the seal in correctly for a fee.