I posted 2 weeks ago that my 93 vert ZF6 broke down on me. It needed a flat bed tow home.

I was in the middle of 4th gear with the gas pedal to the floor (app. 110 MPH). All the sudden, it seemed to slip out of gear and acted as if it was in neutral. Since the gas was to the floor it hit the rev limiter. I put the clutch pedal in and nursed it to the side of the road.

No gears (including reverse) worked. Anytime Id try to put it in gear and release the clutch Id get a nasty grind. The engine ran fine as long as the clutch pedal was pushed to the floor.

When I put the car on jackstands (in gear) I could easily rotate one of the rear wheels by hand. It would move easily during part of its rotation then seem to bind up a little, requiring more force to move it past certain parts of the roation. A nasty sound emanated from the flywheel cover. I assumed the clutch (SPEC stage II 4 years/20k old) was broke.

Upon inspecting the clutch disk, I saw no signs of excessive wear.

The throwout bearing appeared ok, however there is a central part on it (in addition to the rotating splined bearing portion) that is also allowing movement. I dont know if this is normal or not. I guess i should inspect the old one I saved from when I replaced the stock clutch 4 years ago.

I really hope its not the stupid ZF6 transmission. I would rather have blown an engine (and get to rebuild it better) than mess up a transmission. Everyone in my life has led me to believe the only replacement item of a manual transmission car is the clutch.

If anyone has any ideas, please let me know.

Thanks.

 

One thing I want to add is that when I drained the ZF6 GM 5w-30 trans oil, there were no metal shavings or anything like that in the fluid.

 

i am not to familiar with standards but i would guess that you stripped the clutch center are broke the input shaft. anything past the first set of gears in the trans and you would have reverse. probably is the clutch center i assue the noise is comming out of the transmission area make sure you didnt break a u joint?

 

Ive already taken it apart and the clutch center looks fine to me.

I need to look at the transmission somehow to see if its broken. Unfortunately, I dont think theres any way to get inside the case.
There were 0 metal shavings in the ZF6 tranny fluid.

Driveshaft/U-joints did not have any play in it.

 

Is it possible you blew the rear?Does the driveshaft turn when you turn the wheels?

 

when I turn the yoke of the driveshaft the wheels turn.

 

sorry to say but any trans shop is going to charge you around $350 to look at it. I would inspect the pressure plate. I had a Jeep once that some days would shift as if new and other day not want to go into gear at all. It turns out the forks/fingers on the pressure plate were bent so I changed the clutch no problems, by the way the clutch looked fine

 

My goal is to not have to pay some cretins to diagnose whats wrong with my car.

With corvetteforums help (thanks guys)...I do the work myself so the corvette tax rip-off artists dont get any of my cash.

 

so the trans input shaft splines are ok too? If you put the car in gear can you rotate the driveshaft at all?

 

The trans input shaft splines are ok.

The clutch disk splines are ok. THe pressure plate splines are ok.

Before taking it apart, when I turned the rear wheel w/ car in gear(Which turned the driveshaft) the driveshaft would move.

However, at some point along a given revolution of the rear wheel, resistance suddenly increases and there is clunking type noises.

 

if the rear is ok and the clutch is ok then you should check the pressure plate and dual mass flywheel, its possible that they could have broken loose internally (its remote but possible).
other than that all I can think of would be that its not selecting gears (check shifting linkage, you should be able to feel it engage a gear) or as someone has said already, broken input shaft or other major transmission problem.

 

damn... dude... you have such bad luck with this driveline.

I would check every component of the clutch... but the Helm does show how to crack the case on the ZF.

it is a good sign that there is no metal in the oil, but, if a shaft sheared cleanly, that would explain a lot. Can you turn the input shaft and make the output shaft turn?

if it IS the ZF, I would send it to Bill and let him make it perfect.

 

It sounds as though you've satisfied yourself that all's well with the drivetrain beyond the transmission.

Have a good look at the dual-mass (and make sure you didn't shear the flywheel/crank bolts). If all looks good there, and you're sure the clutch is okay, you're almost surely looking at a problem in the ZF.

Be well,

SJW

 

Bill's prices to do this are beyond what a new ZF6 purchased from gmpartsdirect.com would cost.

 

transmission selects gears fine.

Ive already got the clutch disk out. I replaced the dual mass flywheel with a single mass flywheel so that takes some of the complexity out of my problem.

Im going to spin the input shaft and have a friend watch the splined output shaft to see if it moves.....

 

yea, but with the rate you are chewing these things apart, would it not make sense to invest in something that won't blow up?

 

souds like you have been checking alot. my guess is you broke the input shaft. have the car off the ground and turn the rear tires watch the driveshaft move to confirm its not in the rearend have the car in a gear any gear if you can still move the tires and the drivshaft is turning then your problem is internal i would have someone look at the clutch while your turning the back tires to make sure nothitng in the clutch is moving you should be able to see if the input shaft is moving if its not the your problem in internal in the trans and being you said you had no gears it has to be the input shaft. thats what i would check

 

I did a test on the transmission last night.

I shifted it into 1st,2nd,3rd,4th,5th,6th, Neutrail and reverse.

I spun the input shaft once completely around and watched the output shaft spin however many times around for that gear.

Everything appeared normal. There were no unusual noises, bind ups or anything.

I think its entirely clutch/flywheel related....

I appreciate all the advice on here. I do want to point something out, some people are posting like my car is still together and I should do this-and-that. I clearly stated in the post that the car has been taken apart.

 

I did a test on the transmission last night.

I shifted it into 1st,2nd,3rd,4th,5th,6th, Neutrail and reverse.

I spun the input shaft once completely around and watched the output shaft spin however many times around for that gear.

Everything appeared normal. There were no unusual noises, bind ups or anything.

I think its entirely clutch/flywheel related....

I appreciate all the advice on here. I do want to point something out, some people are posting like my car is still together and I should do this-and-that. I clearly stated in the post that the car has been taken apart.