Clutch Problem, Adjustment Changes Options

[Bruce Hinds]

I reinstalled the engine after a rebuild and for some reason that I can't figure out the clutch seems to go out of adjustment when the car warms up.

I park it and let it cool, the clutch works just fine. Pedal play and everything is normal until it warms up again. Seems to be a bit more play but when warm I can't get first or reverse with grinding. Starting in gear with the clutch in, the car still moves.

How can this be?

[914Sixer]

Bushing tends to crumble under heat. I do not know personally but I have heard the new clutch cables are not what they used to be. Perhaps some stretching is starting to take place.

[Bruce Hinds]

Bushing tends to crumble under heat. I do not know personally but I have heard the new clutch cables are not what they used to be. Perhaps some stretching is starting to take place.

But here again, I go out the next day to do the adjustment and it's fine, shifts like butter. 10-15 miles down the road its "like" the cable stretched, but wait a few hours and it's fine.

The old cable didn't have too many miles on it but replaced it anyway. I got the one from 914 Rubber, made by GEMO. That doesn't appear to be the problem though,

[Superhawk996]

Bushing tends to crumble under heat. I do not know personally but I have heard the new clutch cables are not what they used to be. Perhaps some stretching is starting to take place.

But here again, I go out the next day to do the adjustment and it's fine, shifts like butter. 10-15 miles down the road its "like" the cable stretched, but wait a few hours and it's fine.

The old cable didn't have too many miles on it but replaced it anyway. I got the one from 914 Rubber, made by GEMO. That doesn't appear to be the problem though,

Sounds an awful like you’re right in the cusp of not having it adjusted tight enough. When clutch, pressure plate, and linkages and cable get warm it becomes no-go situation until things cool a bit.

Have you tried tightening the cable more?? There is a lot of room between just barely working (as you describe) and it being so tight that you’re preloading the throw out bearing, partially loading the the pressure plate and beginning to slip the clutch

The other thing is to make sure the stop bumper on the plywood floor board isn’t preventing you from getting full clutch pedal travel.

The other thing to consider is that shifting ease will change based on the temp of the gear oil in your trans. When oil gets hot, and things expand, the synchros become less effective. I’d tighten the cable more. If the issue continues and you’re convinced you have the linkage adjusted properly, it may be time to consider looking in the transaxle at synchros.

If it was perfect before the cable swap and then went to (IMG:style_emoticons/default/stromberg.gif) then focus on the cable adjustment and disregard the synchros.

[Bruce Hinds]

Bushing tends to crumble under heat. I do not know personally but I have heard the new clutch cables are not what they used to be. Perhaps some stretching is starting to take place.

But here again, I go out the next day to do the adjustment and it's fine, shifts like butter. 10-15 miles down the road its "like" the cable stretched, but wait a few hours and it's fine.

The old cable didn't have too many miles on it but replaced it anyway. I got the one from 914 Rubber, made by GEMO. That doesn't appear to be the problem though,

Sounds an awful like you’re right in the cusp of not having it adjusted tight enough. When clutch, pressure plate, and linkages and cable get warm it becomes no-go situation until things cool a bit.

Have you tried tightening the cable more?? There is a lot of room between just barely working (as you describe) and it being so tight that you’re preloading the throw out bearing, partially loading the the pressure plate and beginning to slip the clutch

The other thing is to make sure the stop bumper on the plywood floor board isn’t preventing you from getting full clutch pedal travel.

The other thing to consider is that shifting ease will change based on the temp of the gear oil in your trans. When oil gets hot, and things expand, the synchros become less effective. I’d tighten the cable more. If the issue continues and you’re convinced you have the linkage adjusted properly, it may be time to consider looking in the transaxle at synchros.

If it was perfect before the cable swap and then went to (IMG:style_emoticons/default/stromberg.gif) then focus on the cable adjustment and disregard the synchros.

It was perfect before the engine rebuild, BUT even though the tranny had a recent rebuild prior to being parked. It had been parked for 14 years in the garage. I'm embarrassed to admit, I've not changed the gear oil, my reasoning that warmer oil should shift easier not harder. I have adjusted the clutch tighter a few times, my next step is to change out the oil, almost afraid to see what comes out if that's the problem.

[Superhawk996]

It was perfect before the engine rebuild, BUT even though the tranny had a recent rebuild prior to being parked. It had been parked for 14 years in the garage. I'm embarrassed to admit, I've not changed the gear oil, my reasoning that warmer oil should shift easier not harder. I have adjusted the clutch tighter a few times, my next step is to change out the oil, almost afraid to see what comes out if that's the problem.

Don’t underestimate cable stretch and thermal expansion of a long cable. Some of the clutch cables out there will virtually run out of adjustment thread before they are tight enough. Not uncommon to need a spacer to get it to adjust properly.

With respect to the ground strap - make sure you have a ZERO ohm connection. A bad ground will use the starter clutch cable to draw starter current (up to hundred or more amps) through it. This occurs right as you have the clutch pushed in when starting. The cable heats up and stretches as all that current flow through it. Likewise the heat cycling of the clutch cable being used as a ground eventually causes it to become brittle and snap.

A ground that looks good may not actually be good. Many of these braided ground straps are 50 years old and need to be replaced to get a solid ZERO ohm ground between the body and the engine/starter.

I agree though that the ground strap is a long shot since yours seems to recover when it cools. Posted more for the benefit of others that may not understand how a bad ground strap causes cable stretch.

[Bruce Hinds]

It was perfect before the engine rebuild, BUT even though the tranny had a recent rebuild prior to being parked. It had been parked for 14 years in the garage. I'm embarrassed to admit, I've not changed the gear oil, my reasoning that warmer oil should shift easier not harder. I have adjusted the clutch tighter a few times, my next step is to change out the oil, almost afraid to see what comes out if that's the problem.

Don’t underestimate cable stretch and thermal expansion of a long cable. Some of the clutch cables out there will virtually run out of adjustment thread before they are tight enough. Not uncommon to need a spacer to get it to adjust properly.

With respect to the ground strap - make sure you have a ZERO ohm connection. A bad ground will use the starter cable to draw starter current (up to hundred or more amps) through it. This occurs right as you have the clutch pushed in when starting. The cable heats up and stretches as all that current flow through it. Likewise the heat cycling of the clutch cable being used as a ground eventually causes it to become brittle and snap.

A ground that looks good may not actually be good. Many of these braided ground straps are 50 years old and need to be replaced to get a solid ZERO ohm ground between the body and the engine/starter.

I agree though that the ground strap is a long shot since yours seems to recover when it cools. Posted more for the benefit of others that may not understand how a bad ground strap causes cable stretch.

Thanks for the conversation Peter - actually went to HS in Greenlawn, NY with a guy of the same name.