1995 Coupe 63k miles (sons car)
Any of you guys experienced this in the ZF? Fluid level is good, new GM Synchromesh about 30k miles ago. Clutch master and slave replaced within the last 2 years. All forward gears are meshing fine. It doesnt happen every time, but its more frequent. Would it be a good time for a full synthetic?
TIA

 

GM or Royal Purple Synchromesh?

If you used Royal Purple Synchromesh you are wrong. The RP Synchromesh is for Manual Transmission that require ATF as a lubricant.

The ZF uses 5W30, Amsoil Manual Synchromesh and others use Castrol TWS.

 

I have seen grinding if the engine is idling in neutral (clutch out) and then shifted into reverse. The reason it does this is that the input shaft in the transmission is spinning and there is no synchro for reverse.

The way to avoid the grind is to put it in one of the forward gears first before going into reverse.

Sometimes you'll get a grind if you don't depress the clutch pedal far enough to fully disengage the clutch.

 

GM brand

 

Yea, Im starting to think the clutch might be wearing at 64k miles.... Im going to put it on the lift this weekend and look at it a bit closer.

 

Reverse is actually synchronized in the ZF-6. It shouldn't grind even if you are moving slightly forward while you shift into reverse. Sounds like the clutch is not releasing in full.

Try pressing the clutch and waiting 5-10 seconds for a full spin down of the trans. If it goes in easily then without grind I'd bet the money in the bank that the clutch is not releasing 100%. Does it engage smoothly while the engine is off?

 

I have always put a manual trans into a forward gear before going into reverse; just an old habit from years of living with Muncie and B-W T-10 trannies.

Check for any leaks around the clutch master or slave. If there is air in the hydraulic line, that may cause the light grinding. Might be worth bleeding the system and go so far as to replace all the fluid.

If the current clutch has 64K, it probably shouldn't be an issue, but how does your son drive the car? "Spirited"? Do you live in an ares with lots of hills and heavy city traffic?

 

Sorry guys been working allot lately. Ill have the car up on the lift this weekend and report back when I do.
Thanks for the help and suggestions!

 

Though most will advertise that 30k on a tranny fluid is fine, my experience is otherwise. The factory fill GM fluid in my 06 CTS-V sheared low out of viscosity grade in about 10k miles.
2006 Cadillac CTS-V Used Oil Analysis Dexron III vs AMSOIL ATF Transmission Fluid

AMSOIL's recommendation for your tranny:
AMSOIL Synthetic Synchromesh Transmission Fluid (MTF) (Product Code MTFQT)

 

Ok, so my son & I had a chance to work on the 95 yesterday. Started at the clutch master and worked our way down.

Clutch master was dry inside the car and outside in the engine bay. Fluid level was good, but a bit dirty, so I turkey basted it out and refilled.

Line to slave in good shape, no leaks.

Slave itself was dry BUT, the bleeder screw/valve was pretty loose. I noticed fluid on the threads. Funny that the level was good in the master however... anyway, tightened it up.

Transmission was very dry, no sign of any leaks or even seepage. Oil level was perfect and the fluid looks nice and golden in color.

Clutch pedal travel seems right on. I went through the gears with the engine off, normal.

I went through the gears on the lift, engine running, also seemed fine, no grinding.

NOTE** I do notice a whine which seems to come from the throw out bearing with the car at idle, clutch out. As soon as you push the clutch in, the noise stops. But, as I said, the operation and travel seem fine. My son says the noise has been there from day one when we bought the car 3 years ago.

So we wrap everything up, my son puts it in reverse and its good. I say try it again just to see,,,, GRIND!! He says when it does it, it feels like it goes into gear, then he lets the clutch out a little, thats when it grinds.

Were stumped at this point and Im not sure what to check next. The tranny does have the 1-4 skip shift eliminator installed... not sure if thats any issue....All the forward gears shift perfectly.

Help!!

 

If the bleed valve on the slave cylinder was loose and you saw some indication of moisture, it's possible that air has gotten into the slave. That can keep the clutch disc from being fully released and causing the grinding.

Bleed the system to insure there is no air in the slave cylinder. Good idea to flush out all the old fluid at the same time. You can use a DOT3 or DOT4 brake fluid. Even though the reservoir has fresh fluid from the turkey baster method, it won't be long before it turns dark again.

The skip shift eliminator will have no bearing on the grinding issue.

 

I am confused; does it grind when you're PUTTING IT INTO rev...or after you think it's engaged, and you apply a load (start to release the clutch pedal)

As stated above, the ZF has a synchronized reverse so it shouldn't grind GOING INTO reverse. If it does grind under that circumstance, then either your clutch is not releasing all the way, or the rev. synchro is shot. Assuming that it is grinding when trying to put it into reverse, here is how to diagnose between those two:
Jack the rear of the car, start engine and put it into gear. With the clutch pedal fully depressed, the wheels shouldn't move. If they do, then the clutch is dragging/not fully releasing.

If the wheels don't move at all, then the problem must be the reverse synchro. You can avoid the grinding (going into gear) by bumping any of the 6 forward gears first, then going to reverse.

If the problem is grinding AFTER you think you have engaged reverse, then there is either something wrong with the shifter/linkage, or something inside the trans. Either would require disassembly to inspect/diagnose.

 

Its more of a situation where he says he thinks its in gear, then starts to let the clutch out and it grinds at that point. He has been dealing with it for a while now and says hes starting to realize what feels like an interference when putting it in reverse.... when he does realize its happeneing, he shifts into first then it goes into reverse easily.....

 

Run the test that I described above. That will give you clarity as to the releasing of the clutch.

 

Ok, thanks. My son will be here later on today, Ill try it.

 

Sounds like the same problem i have with my 95 vert. May even be jumping out of reverse or not going all the way into reverse. It dose this when i start to release the clutch. About 1/3 of the tlme and only in reverse. Haven't had time to check it out yet. Only had the car about 4 or 5 weeks.