Clutch Fork Broken or Adjustment Problem?

Alan Lindquist · 08-20-2010, 09:37 PM

1980 911SC with 915 tranny

Need advice before dropping the motor. I suspected a broken or weakened/bent throwout fork but went through some simple checks first. Can anyone interpret what I'm seeing and suggest if it adds up to some worn parts and miss-installed actuator arm or if it's likely that I have a bad fork?

Symptoms: For 14 months since new Sachs clutch installation (self) car shifted fine and pedal felt fine, though engagement was right off the floor. Like as soon as you started to lift your foot. Pedal assembly was groan/squeaking.

Recently and suddenly the pedal developed a LOT of slack. I could feel it coming on for a few days and when it got real noticeable, I took up slack at the trans housing adjustment and the problem was solved. Pedal was now actuating in a better spot (not right off the floor but more towards the middle). Then a week later it was slack again. Went through the adjustment procedure and got it right again, and three days later there's slack. I made an emergency adjustment on the road and got the car home, barely, before I couldn't get enough disengagement to shift.

I started to assume that the fork might be bending and ready to break.

As a first step to diagnose I pulled the clutch cable and it seemed fine but the clevis bushing was only half there and the retainer pin was worn half through. This explains the groaning and squeaking and could explain the need to draw slack.

But under the car I found something more alarming. My keeper spring was in a "rolled" position. In other words, it wasn't tucked against the cutout in the heat exchanger - it was over about half an inch. When I rolled it back to where it should be, I gained ENORMOUS clearance between the adjuster screw and the clutch arm actuator. As you can see in the photo - there is 3/8ths inch gap between the adjuster screw and the arm and running it all the way in full adjusted won't close that gap. The only way to close that gap with ALL the clutch adjustment available, and when you pull it that much, it makes the spring roll out of position when the clutch is actuated.

Can I solve this by removing the retainer clip and rotating the clutch lever over on the spline? Maybe I installed it on the wrong angle to begin with and the car was coping with it till the clevis bushing gave way?

Or is the arm so far out that I should still suspect a broken or bent fork?

sailchef · sailchef's Garage

Quote:

Originally Posted by Alan Lindquist

Can I solve this by removing the retainer clip and rotating the clutch lever over on the spline?

I think this has been the problem all along.

Pedal releasing right off the floor etc. You need to close that gap, and then use the adjuster to micro-tune. Follow the tech article on this site in the "tech section" or refer to your bently's. The clearance there shouldn't be done by eye and the cable has tolerances/specif distance it needs to travel

Gunter · Gunter's Garage

I'd try to move the shorter actuating lever one spline and re-adjust.

But, note that the counter-nut for the adjustment bolt needs to be on the other side of the large release lever; see picture!

Ensure that the clutch cable sits correctly in the tube by the fire wall.

Check all pedal cluster bushings and that the roll pin for the clutch pedal is not sheared off. (Hard to see!)

If in doubt, rebuild the pedal cluster with brass bushings. If the clevis bushing is gone and the clevis pin has worn out the hole, the pedal shaft needs to be replaced. I'd rebuild the cluster before anything else.

And then adjust the clutch according to factory procedure.

Post a picture after you're done showing all including the cable position nuts.

Alan Lindquist · 08-21-2010, 03:34 PM

I did rebuild the clevis bushing. The plastic one was cracked in half and the retainer pin was worn half-through. I now have a brass bushing. It looks to me like the photo you posted shows a longer adjustment screw than I have. If I run mine out ALL the way with the fix-nut on the wrong side - I still can't reach the actuator arm. I'm following Wayne's book - the procedures for adjusting the clutch. I just can't reach with the adjustment screw.

I tried rotating the actuator arm one spline, but it is too far and collides with the spring arm, so that won't work.

The engine is prepped for pulling and I have a friend coming over tomorrow to help me pull it and the tranny. I'll open it up and look at the fork. I bought one just in case.

For now, the clutch pedal assembly is in great shape, the clutch cable is in great shape, the actuator arm is where it needs to be and I have a gap that can't be spanned with the set screw that I have so I have to check the fork.

This was a fairly sudden change. The clutch worked fine for a year after replacement but I used the old fork, and for all I know, it has 200,000 miles on it like the rest of the car.

I'll post again tomorrow after pulling the motor and tranny and having a look. Thanks for the feedback.

Alan Lindquist · 08-22-2010, 06:44 PM

Clutch fork was broken/bent. Replaced. Clutch is butter smooth now.

James Brown · James Brown's Garage

Nice diagnosis and repair.

Gunter · Gunter's Garage

Good for future reference.

Alan Lindquist · 08-23-2010, 01:05 PM

Here's what the broken fork looked like. One serious break and bend on one side, and a crack and bend on the other. A mechanic told me that they rarely break and separate because the distortion stops the clutch from working before you can use it enough to actually break it. It's a bummer on the road, because the best you can do is yank it out of gear and coast to the curb or use the gear you're in to get to a safe spot and then yank it out. If it happens in neutral, you won't get a gear, just grinding - time to get out and push. And you can suspect that you are headed towards this little disaster if you suddenly find yourself adjusting the clutch - especially more than once in a short period of time. The pedal slack is dramatic, not subtle like wear over time.

moneymanager · 08-23-2010, 08:10 PM

A broken roll pin in the pedal cluster can behave exactly the same way. Mine would work for a few weeks, then the gears would begin to grind. I'd adjust it, it would work for a while, then the shifting would get difficult again. When I pulled the cluster, the pin came out in three pieces. Always start with this; it is a $2 fix and pretty easy to check.