Car is an '01 coupe with MN6 and 58k miles. Headers and intake only add ons. Car has never been dragged but has about 3,000 road course (i.e., track) miles.

Was going for a drive about 3 weeks ago and couldn't get in reverse to get out of garage. Managed to force in eventually but then very hard shifting into forward gears. Drove it a bit and it 'fixed itself' and drove fine.

A week later took it out for a 300 mile drive. About 150 miles into drive it got very hard to shift for about 20 miles but again fixed itself.

Today went out and after 150 miles it did it again but worse than ever. Got VERY hard to shift going into 4th, 5th and 6th. Could NOT get into 1st thru 3rd. Had to start from dead stops in 3rd as I was then able to use a lot of force to get it 4th, 5th and 6th. It took less force to get into 4th, less again to get into 5th and less again into 6th. However, even this took enough force I though I was going to break something....

Was able to downshift from 6th to 5th and then 4th. Again with MUCH force. Could not force into 3rd, 2nd or 1st.

Nursed it home with the following observations.

- With the engine shut off it would go into any gear smooth as butter.

- With the car rolling at driving speeds I shut the engine off and coasted but could not upshift or downshift. When car came to a complete stop with engine still off I am able to shift into any gear, smooth as silk.

- I'd come to a light and shut the car off till it turned green. While waiting with engine off put into second or third. Upon green light start the car in 2nd or 3rd with brake on and car would shudder as if clutch wasn't completely disengaged.

- Finally it got to the point that with the brake released and clutch completely depressed the car would creep forward.

When this started 3 weeks ago I thought maybe I somehow got the shift linkage in a bind and it "snapped" back into place as it 'fixed' itself.

Then I thought it was a problem with the transmission, possibly the syncro's.

Now I'm thinking it might just be clutch related.

Should also mention everything seems to work fine once I'm moving in any gear. Problem is getting it moving and being unable to change gears once moving. Clutch doesn't appear to be slipping once moving. Nailing the gas once I get it moving in whatever gear I'm in seems to put the appropriate power to the ground.

I would really appreciate your advice.....

Rick

 

Sounds like you may be low on clutch hydraulic fluid ... first thing I'd check is the fluid level in the reservoir on the clutch master cylinder.

If you have low fluid, air may be in the line, and you will have to bleed the line after topping off the reservoir. Often if the fluid is low, pumping the clutch pedal seveeral times and then trying to engage the gear sometimes works.

That's where I'd start ...

 

It does sound like something has happened so that the clutch is not fully releasing. Does the clutch pedal still feel the same.
I remember once I put in a new clutch and it would drag just enough that I could not put it into first without grinding noises. I could shut the car off, put it into gear, and start it in gear. Once I was moving, everything seemed fine.

 

1. Hydraulic fluid in reservoir is at the same level as the day it bought the car.

2. Pedal feels exactly as it has for the last 30k miles.

Rick

 

Hmmmmm ..... it sure sounds like the clutch .... especially when you say that ....

"Finally it got to the point that with the brake released and clutch completely depressed the car would creep forward."

That's a pretty clear sign the clutch is partially engaged .....

If the fluid is full, either the clutch master cylinder is defective, or the clutch "Actuator Cylinder" (also known as the slave cylinder, the part that converts the movement of the fluid to the mechanical force on the release bearing) is failing .....

In next post I'll list the diagnostics from the service manual .....

 

1) Check for restricted pedal travel (floor mats)
2) Test for air in the hydraulic system
3) Bleed the hydraulic system
4) Inspect the master cylinder for worn seals
5) Remove trransmission and inspect slave cylinder for wear
6) Replace slave cylinder
7) Inspect clutch assembly for
...... Damaged or worn clutch driven plate
...... Binding on the clutch driven plate
8) Replace the clutch disc.
9) Install transmission and test car

and the numebr ten step is ......

10) Replace car

Ooooopppsss ... only kidding on #10 .....

 

^^I had a similar problem with my car and it turns out I probably have a bad slave cylinder. There have been a lot of posts about problems with the slave because of its location (very close to high heat source) and just the general design.

I would try to take a closer look at the slave cylinder.

Here is a link to a really good thread on the subject.

http://forums.corvetteforum.com/show....php?t=1763721

Hope you are able to find and fix problem soon.

 

Rick,

It sounds like a clutch issue. I was having a similar problem with my car, only not as severe. For reference, I have an aftermarket clutch (Luk Pro Gold) and shifter (Hurst). It started out being difficult to shift into reverse and first and then became difficult in every gear. My mechanic flushed the clutch fluid and that didn't help. Then he checked the shifter alignment and found that the rubber bushing/dampner between the shifter and transmission had disintegrated. He replaced that and it went back to just being difficult to shift into first and reverse.

I talked to TJ at RPM because I thought it was my transmission (after the previous things I mentioned didn't solve the problem). After talking to TJ, he was convinced that it was my release point on my clutch. He said that my transmission might also be damaged and need to be rebuilt but that I need the adjustable master cylinder first. I ordered a Mcleod adjustable master cylinder for the clutch and my mechanic installed it. It seems to have fixed the problem. I may still have to have the tranny rebuilt down the road...but it for now it shifts into every gear fine.

 

I'm not really sure how the slave cylinder functions but could it be "hanging" up intermittently and not exerting pressure to release? Is it a "piston" which could have an issue?

Rick

 

Rob,

What would make you believe it's the master cylinder and not the slave cylinder? Isn't the master cylinder just a reservoir with a hose running out of it to the slave cylinder?

Rick

 

Thanks for the response. You stated:

^^I had a similar problem with my car and it turns out I probably have a bad slave cylinder. There have been a lot of posts about problems with the slave because of its location (very close to high heat source) and just the general design.

You say you "had" a problem implying you fixed it?

You also say you "probably" have a bad slave cylinder.

What makes you believe it's the slave? Did you replace? Did it fix your problem or is your problem intermittent and you're just living with it?

TIA

Rick

 

No ... the master cylinder is not just a reservoir with a hose running out of it ......

You have TWO ... count them .... TWO master cylinders in your car ..... one for the brakes, the other for the clutch.

Both work the same way. When you step on the pedal, you are pushing a piston down a cylinder (hence the name master CYLINDER) and the piston pushes hydraulic fluid into a sealed line. At the other end of the line the "slave cylinder" has a piston that is moved by the increased pressure of the hydraulic fluid, and the piston moves against something. In the case of the brakes, the "slave cylinders" are the brake calipers, and you are pressing the brake pads against the rotors. In the case of the clutch, the slave applies pressure to the release bearing to disengage the clutch.

So ... going back to what I originally posted ... CHECK the CLUTCH reservoir for fluid ..... there are two reservoirs .... brake and clutch .... make sure the CLUTCH reservoir is full.

Second, as I listed in post #6, if the reservoir is full and you are sure there is no air in the hydraulic line (air bubbles compress when you create pressure on them ... so a master cylinder can't pressurize a line that has air in it ... the slave cylinder doesn't respond to zero pressure ...) then you need to remove and disassemble the CLUTCH master cylinder to see if the seals on the piston in the cylinder are worn out. If they are worn then the piston can't generate pressure. If they are OK, then you have to drop the drivetrain (differential, transmission, and torque tube) from the car to inspect the slave cylinder and clutch mechanism.

If you have low fluid in the clutch reservoir .... there is good news and bad news ....

The good news is it is relatively easy to fix (I say relatively because getting to the bleed screw is a PITA), just add fluid and bleed the system.

The bad news is that low fluid indicates a leak, and at some point the leak will get worse and need to be fixed.

 

I'M just going to jump in with a few suggestions.. first thing I would do is replace the transmission fluid....
secondly hydraulic fluid is hygroscopic ( not hydroscopic ) this can really undermine the fluid in your master cyclindars, if the stuff is real black and funky, I would change it... the reason I say this is because the OP has done road course events,, that alot of on the brakes and off the brakes.. the fluid get very hot... you need a good 250+ 300 degree fluid .. I would do the easy things first... change the trans fluid.. and get some good brake fluid ( here is an ET tip ) the best bank for the buck in brake fluid is go to a ford dealer and get their brake fluid, it has the highest boil rate offered at the lowest price...

Good Luck
Bill aka ET

 

Oh, my gawd...that'll generate some discussion!!! Good tip...

 

Bill,

Thanks for the reply. I offer:

1. Transmission fluid was changed less than 10k miles ago to Royal Purple, I believe Synchro Mesh or whatever most on this Forum recommend.

2. I run ATE Super Blue racing fluid for my brakes. I will give this a shot in the clutch system. BTW, current fluid is not real nasty looking.

Rick

 

Black Z06,

Thanks. I wasn't thinking when I responded. I'm thinking I have an issue with either my master or slave....

Rick

 

Bill,

Provided my tranny fluid and clutch fluid are not the problem, what is the next thing you suspect is the culprit?

Rick

 

There is some thoughtful advice in this thread.

My suggestion is that it's likely the clutch hydraulics at issue. In order, these are the steps I'd follow.

(1) thoroughly clean the clutch fluid following this procedure: Maintain Your Clutch You want to rid the accumulated crud from the clutch hydraulics. May not work; but the investment is about $10 and an hour of your own time.

(2) replace the clutch master cylinder. The seals may be compromised. At 58K miles it's a distinct possibility unless you've kept you clutch fluid free of debris throughout the life of the car. Dirty clutch fluid is saturated with clutch dust which constitutes an abrasive that attacks the integrity of seals within the hydraulics. Cost of parts and labor is about $300. Far cheaper than the next step.

(3) replace the clutch actuator (slave) along with all the rest of the clutch parts (less the master cylinder). Most of the cost is labor. May as well replace everything, not just the slave.

If you must progress to step #3, pick your shop very carefully. Lot of sad stories in the CF archives here on botched clutch installs and post-installation vibrations.

Good luck and let us know what you find.

Ranger

 

If the brake fluid is not bad looking that would more than likely eliminate that... Royal Purple is good stuff for the trans.

Without a slave bleeder its tough to do the deed. If you have never changed the clutch fluid, and did all that road course stuff, that could be your problem
My next thought would be shifter bind. Do you have an after market shifter?

 

Sometimes not seeing the forest through the trees is the problem... I personally do not suspect, Fluid, Slave, or Clutch Mechanics...

I'd lay a bet the shifter linkage is Fecked....it got out of adjustment..When its really bad shifting is a nightmare.

One time I got me car back from a clutch job and the shifter was so far out of whack I needed 2 hands to get it in reverse.

One indication something aint right is is the shifter seems to lean a bit to the passenger side of the car...

There is a procedure that entails taking the center console out to expose the shifter... Then you need to put the shifter alignment pin in, then losen the the shift rod bolts.. while it's all lose, pull the alignment pin and wiggle the shifter vigorously, that will take any binding out of it... Then resposition the shifter so the alignment pin slides back in.. shifter should be look fairly straight.. Tighen the bolts and and PULL the alignment pin.

JMHO