Vanishing Clutch.....
 

Eleven years ago I swapped the Turbo 400 out of the GTO and a TKO600 in. I'm guess the car has traveled 20,000+ plus miles since. I used a hydraulic clutch setup. Recently where the pedal takes up in the pedals travel has dropped closer to the floor, but I'm not sure its completely because the clutch is worn. I tried bleeding the hydraulics and really didn't see a change. Last night I took the car for a ride and after starting it, getting the TKO into reverse was tough. Hard mash into the floor did it. Into 1st was fine, but pedal at the floor, and pulling off and clutch modulation was not problem. No issues during the 30 mile ride....until....I pulled out from one country road onto another, ran it gently through 1st gear, shifted into second and then rolled into it. Redline shift, hard through 2nd gear and then I couldn't find 3rd. I went to neutral and coasted a while and tried to find 5th. Nope. I found 4th and then 5th and headed home. Finding any gear was tough, but I got home. I left the GTO out while I did some stuff in the basement and then really struggled to get reverse and then 1st to pull the GTO into the basement. As this has played out over the last few weeks I initially thought the clutch was worn, then gradually I've changed that to the master or slave cylinder giving up. Pulling through the gears yesterday there was no hint of slip.


For some reason I ended up with 2 master cylinders as I installed the TKO (thank you Keisler) and I think I'll start putting the unused one in Saturday morning. Try the easy stuff 1st.

My TKO has ground 3rd from day one.

Car have a reinforcement plate on the inside of the firewall where the MC bolts up?

Clay

It has a plate, but it's on the outside, IIRC. I did check the fasteners, all tight.

Plate have its own bolts with big washers on the inside?

Clay

my recollection is that worn clutches engage later, not sooner ...

Clay, I'll have to look when I get home.

Makes sense.

Should have asked first... Is it using/losing any fluid?

Clay

I haven't noticed the level drop at all. It was at the mark I have on the reservoir when I bled it a while back and it is still there.

Classic signs of clutch not getting fully disengaged. In your case, due to a faulty slave on the clutch or faulty clutch MC. Worn plate would make no difference, just like brake pads: the fluid will 'take up' the difference for a consistent pedal feel and travel. I would suspect your MC or your slave is bleeding down. I personally would not have any aftermarket hydraulic clutch/slave actuator. Too hard to change when they fail. BTDT and trans R&R is not on my 'fun' list. Since your fluid in the MC is good, it's possible it's internally bypassing, just like a bad brake MC.

There is a plate on the inside, I remember drilling it out to accept the end of the master now. All seems like it’s always been.

The pedal doesn’t feel like it used to. One coolish morning before long I’m going to pull the master out for a look. It’s fairly easy to accesss.

Been thinking about this. Suspect it is bad M/C allowing fluid to bypass the piston when you press the clutch. This would explain why it works better when you "stab" the pedal, less time for fluid to bypass. And also why the fluid has not dropped.

If it was the slave cylinder I would expect a leak.

Just my $0.02 from far away.

No leaks, which for a Pontiac, is kinda odd in itself. :) The 50 year old rope seal might shed a drop on the garage floor once a month. Nothing else leaking though.



Thanks guys.

Have seen jam nuts on adjustable pushrods work loose.

More you worked the pedal the shorter the rod got.

Eventually getting short enough that the clutch wouldn't disengage.

Clay

I pulled my Keisler install package down last night, so I could check that before I started taking things apart.

Thank you Clay.

Again, the clutch master cylinder can leak internally, by-passing, just like a brake master cylinder. You won't lose any fluid and it won't leak externally, but it will let fluid past the piston in use, and you will get the symptoms you are experiencing. (Insufficient clutch disengagement).

Hopefully I can get a few minutes to start looking at it tomorrow morning. I'm going to take the adjustable push rod loose and verify that it is the right length, since that's the easiest thing to do. If that passes, the master is next.

I wedged myself under the dash and had a look at the adjustable clutch pushrod. Having had a (well…..6 actually) reverse replacement right shoulder procedure, getting under there is a hoot. The rod is right where I left it years ago. The stop is against the rubber bumper as it’s supposed to be. I did watch the action of the rod and there is a slight shift (side to side) in the movement in the master cylinder rod both going in and coming out. Some sort of slop.
Master cylinder coming out next.

I swapped out the master....finally. Now when I can round up a helper, I'll get it bled. Including my first grandchild, lots of things on my plate lately and the GTO seems to be at the bottom of the need to do list. Temps cooling off down here at last. My working in an 85+ degree garage "want to" is low......:)