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Advice on ’96 ZF clutch needed...

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
1,610
Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
Hi, Everybody.

I think I may need a new clutch in my ’96. Here are some of the things I am experiencing; I was wondering if those in the know could weigh-in with your advice. With the symptoms I have below, does it sound like it's time for a new clutch or is something else amiss?

  • When I press clutch in, I will hear a “click” come from underneath the car, sounds like it’s coming from just ahead of the clutch pedal or bell-housing area. Sometimes its a single “click”, other times, I hear three distinct “clicks”.

  • It can be hard to get the car in reverse at times. It’s intermittent. Occasionally, it will go into reverse and there will be a loud “clunk”. Most of the time, it goes into reverse with no problems.

  • The car shifts fine and does not slip gears

  • I have 53,000 miles on the car, it is the original ZF OEM unit

  • I know the GM OEM dual mass flywheel has been discontinued, any recommendations?

Any advice would be appreciated!

B17Crew
:w
 

nickyg

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Apr 9, 2006
Messages
43
Location
Taylors, SC
Corvette
1994 C4 Black on Black 6 speed
If you're not slipping in any gear, it sounds like you have an initial engagement issue. I would first check the fluid in the clutch master cylinder. If low, fill it to proper level. Then, have someone get in the car and step on the clutch while you visually inspect for possible leaks from the master down to the slave. If no leak, then I would do a proper bleeding of the clutch master cylinder.:thumb
 

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
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Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
If you're not slipping in any gear, it sounds like you have an initial engagement issue. I would first check the fluid in the clutch master cylinder. If low, fill it to proper level. Then, have someone get in the car and step on the clutch while you visually inspect for possible leaks from the master down to the slave. If no leak, then I would do a proper bleeding of the clutch master cylinder.:thumb

Thanks, nickyg. I will do that this evening!

B17crew
:w
 

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
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Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
I checked my fluid level in the reservoir. It was about an 1/8" below the FULL line. I happened to have the proper fluid handy and filled it to FULL line. I could not detect any leaks, it was bone dry above and below the car.

Looks like we are going to have good weather tomorrow. I’m going to take it out Sunday and see how it does.

Thanks for the advice, I’ll let you know how it goes.

B17Crew
:w
 

G Winter

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Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
Your description makes me think either bad master cyl or bad slave. If your clutch is bad it would be slipping.It sounds to me like the clutch is not fully disengaging.

Before you try to put it in gear pump the clutch pedal very quickly 6 or 8 times then immediately try to put it in gear. If this improves getting it into gear you have a problem with either the master cyl or the slave cyl.

Glenn
:w
 

89blackvette

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Joined
Feb 7, 2003
Messages
178
Location
Sylvester, Georgia
Corvette
1992 white Coupe
I recently had the same sort of problem with my 89 6 speed. I replaced the slave cylinder and it improved. Then I replaced the master cylinder and it completely fixed the problem, it now shifts like new with no problems. I also replaced the lube in the transmission at the same time. I have noticed that the more knowledgeable people say replace the slave cylinder and master cylinder as a pair, my experience found this to be true. Hope this helped some, good luck with it.
Mike
 

Hib Halverson

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Before I did much more conjecture, I'd get the car up on jack stands, put an assistant in the driver seat, crawl under the car then have the assistant work the clutch pedal. Do that and you'll be able to tell if the noise is coming from the clutch housing (ie: some issue with the clutch) or the slave cylinder, which is mounted on the side of the clutch housing.

The high effort going into reverse may or may not be a clutch issue. Are there any other gears that, when you shift into them, you feel high effort?

The "clunk" when going into reverse might not be a clutch issue at all.
 

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
1,610
Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
Before you try to put it in gear pump the clutch pedal very quickly 6 or 8 times then immediately try to put it in gear. If this improves getting it into gear you have a problem with either the master cyl or the slave cyl.

Glenn
:w

After adding fluid to the clutch reservoir, the high effort with reverse has seems to have gone away. I took the car out today and drove in residential areas that required a lot of shifting (stop signs everywhere). All shifts were smooth and seemed normal. Multiple shifts into reverse seemed normal as well. Not sure exactly what is going on. I will try depressing the clutch 6-8 times and see if I notice any difference.

Thanks!
B17Crew
:w



I replaced the slave cylinder and it improved. Then I replaced the master cylinder and it completely fixed the problem, it now shifts like new with no problems. I also replaced the lube in the transmission at the same time. I have noticed that the more knowledgeable people say replace the slave cylinder and master cylinder as a pair, my experience found this to be true. Hope this helped some, good luck with it.
Mike

This problem I’m having seemed to come on pretty quick rather than gradually. I’ve never had any problems with a ZF tranny before. I don’t have any leaks under the car and the areas around the slave and master cylinders are dry. If there is a problem, I’m hoping that it’s the slave and master cylinders and not the internals of the ZF!

Thanks for your input.
B17Crew
:w



Before I did much more conjecture, I'd get the car up on jack stands, put an assistant in the driver seat, crawl under the car then have the assistant work the clutch pedal. Do that and you'll be able to tell if the noise is coming from the clutch housing (ie: some issue with the clutch) or the slave cylinder, which is mounted on the side of the clutch housing.

The high effort going into reverse may or may not be a clutch issue. Are there any other gears that, when you shift into them, you feel high effort?

The "clunk" when going into reverse might not be a clutch issue at all.

Hi, Hib.

It may be a few weeks before I can get the car on stands, I am going to follow your advice and see what turns up. After adding fluid to the clutch reservoir, the shifting effort into reverse seemed normal again. The fluid was about an 1/8" below the FULL indicator, doesn’t seem like that would be enough to cause the problems I’ve had. I can’t say that I have high effort shifts in other gears. Occasionally, I will have to double clutch at a light when going back into 1st gear though.

It’s been odd... today, everything worked perfectly. The “clicks” when depressing the clutch pedal were non-existent as was the “clunk” going into reverse.

I just hope it’s not the ZF, I cringe at that thought of having an internal problem with the ZF.

Thanks for your advice!
B17Crew
:w
 

G Winter

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Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
Unless you are VERY abusive to the transmission it is unlikely you have a problem with it, they are tough. Seems the majority of the problems I have seen asked about here end up being clutch related. Usually with the hydraulics.

Scav.
:w
 

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
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Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
Unless you are VERY abusive to the transmission it is unlikely you have a problem with it, they are tough. Seems the majority of the problems I have seen asked about here end up being clutch related. Usually with the hydraulics.

Scav.
:w

Hi, G Winter.

I’m use my ’96 for leisurely drives, after a week of the grind, I use it as my “decompression chamber”. I’ve owned it since 1998 and have been pretty easy on the car.

I just went out and did a little test. I started the car and put it in and out of reverse literally 20 times. I noticed about on my tenth engagement I got a little ham fisted when putting it into reverse, the engagement was difficult and I got the loud “clunk”. I made it a point to do light effort movements to crash the reverse gate and it was like a knife through butter smooth.

I don’t know if it's possible that I’ve put too much effort a few times putting into reverse and that may have caused the “clunk”?:confused
The “clicking” when depressing the clutch pedal has not resurfaced since I refilled the clutch fluid in the master cylinder. Because of work demands, I’ve been unable to drive the car with regularity. Maybe once every two weeks I can exercise the car. Could that be a contributing factor?

B17Crew
:w
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
What does the fluid look like? Is it clean or does it look a little dirty?
If you have nobody to help ,open the bleeder on the slave then watch the master cyl. It should drain when it gets down a ways (not empty) fill it , do this a few times so the fluid gets changed. If you have someone to help you could do the traditional bleed quicker. It is amazing how dirty brake and clutch fluid can get. BTW the clutch used diff fluid than the brakes.

Glenn
:w
 

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
1,610
Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
What does the fluid look like? Is it clean or does it look a little dirty?
If you have nobody to help ,open the bleeder on the slave then watch the master cyl. It should drain when it gets down a ways (not empty) fill it , do this a few times so the fluid gets changed. If you have someone to help you could do the traditional bleed quicker. It is amazing how dirty brake and clutch fluid can get. BTW the clutch used diff fluid than the brakes.

Glenn
:w

In July, I replaced the clutch fluid. I used a syringe to withdrawal the fluid from the clutch master cylinder. I used GMs clutch fluid that I purchased from the local Chevy dealer. The fluid seems to be clean, it is currently a reddish-brown.

Unfortunately, I won’t be able to look over the car until one or two weeks because of work. I will report back what I have done and the outcomes, I’m anxious to try the recommendations that have been posted here. Be nice to remedy this at home rather than in service department.

Thank you for the advice!
B17Crew
:w
 

B17Crew

Well-known member
Joined
Oct 8, 2002
Messages
1,610
Location
Columbus, Ohio
Corvette
96 LT4 Polo Green/Light Beige Interior
I wanted to report back to everyone on the outcome of the problem I was having with the “clicks” and “clunks” with my ’96.

I took my ’96 to Corvette Care, Inc. They’ve repeatedly been listed in Corvette Fever’s annual “100 repair shops you can trust.”

Lloyd Harvey, the owner, is knowledgeable about Corvette’s and runs his business in an honorable way that is hard to come by anymore. I can’t say enough good things about this Corvette only service facility and its owner.

Turns out all that was needed was a bleeding of the hydraulic system. I had replaced the fluid in the master cylinder in the spring and not bleed the system. Since the bleed of the system, all problems have gone away. It’s as smooth and quiet as if nothing had ever happened. The transmission is in A1 shape and the clutch is in perfect working order. Let me tell you how relieved I am that it wasn’t the ZF!

If you are in the central Ohio area and are in need of a reputable Corvette service facility. Without hesitation I recommend:

Corvette Care, Inc.
2648 Ferris Road
Columbus, OH 43224
p: 614-471-3331
Owner, Lloyd Harvey

I’d like to thank all you who offered advice and direction.

Happy Thanksgiving!
B17Crew
:w
 

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