Clutch Cable Adjustment Problems

[TargaWoods]

Fixing up a 78SC

It was driven harshly for 25k miles, had the clutch rebuilt. Then had another 10K miles put on it, then it was barned from 2000-2021.

-Replacing the clutch cable
-I did the factory adjustments of 1.2mm with nothing connected
-Connected the clutch cable, had the pedal have 1" of free wiggle with the clutch cable transmission nuts completely loose
-I then tightened down the transmission nuts until the screw gap was 1mm.
-slack in pedal was taken out (as expected)

while the car was still on jacks, I got in, tried the reverse gear test, it ground just like the last 4 times (much disappointment)

For fun, while on jacks, I tried shifting to 1st, 1st worked, 2nd worked, all the way to 5th, and back down.

For the first three adjustments, all gears ground, this is the first time I've been able to get 1-5 working.

Is my adjustment out of wack? Is 1-5 only working because they have synchros to assist me? Is reverse gear in the tranny just screwed up?

How do I get her rolling.


P.S. Whenever I adjust the screw, and then press the pedal, the clutch fork comes back down flush with the screw, with the 1mm gap disappearing, is this supposed to happen? or am I horribly out of adjustment.

[911obgyn]

Sounds like shifter linkage, bushings, adjustment.
One thing always leads to another. I think your clutch adjustment is correct.

[TargaWoods]

How could the shifter be maladjusted if works with gears 1-5 but not with reverse?

Not saying you’re wrong, just trying to understand how Porsche did it.

I’m going to try adjusting the tension on the trans nuts a half turn tighter or looser and see if it does anything while the engine is running.

The travel was 25mm on the dot, going to see how changing it changes it.

[Otter74]

The motions of the lever in your hand being translated to the correct motions at the shift rod depends on the bushings in the linkage being good enough to locate it correctly. There is a bit extra force (over what you'd use for 5th) required to push the lever into reverse, and that might be enough to make bad bushings become a problem. I'm not saying it is, but it's plausible, especially if the car hasn't seen any attention in 22 years. The bushings are cheap and getting them in and out is a bit obnoxious but not overly hard. It's worth verifying condition and addressing as needed in any case.

[911obgyn]

Can you shift into all gears with while engine is off just sitting?

[TargaWoods]

Originally Posted by 911obgyn

Can you shift into all gears with while engine is off just sitting?

100%, have always been able to. The problem with shifting appears only when the engine is running.

[PeteKz]

You may have adjusted the clutch cable "correctly," but I've had similar issues on cars in the past. Try adjusting the cable until you have no free play. See if it grinds going into reverse. If it doesn't, then back off the adjustment until you barely don't get grinding. Over time, the clutch wears and the "engagement zone" tightens up, and then you can readjust. IF it still grinds after adjusting too tight, then something might be wrong with the clutch. Was that replaced recently?

Try over adjusting it first and let things settle in for a thousand miles or so, then readjust.

When it's up on jacks, do the rear wheels turn with the tranny in gear, with the clutch pedal pressed down?

[David Inc.]

Originally Posted by PeteKz

You may have adjusted the clutch cable "correctly," but I've had similar issues on cars in the past. Try adjusting the cable until you have no free play. See if it grinds going into reverse. If it doesn't, then back off the adjustment until you barely don't get grinding. Over time, the clutch wears and the "engagement zone" tightens up, and then you can readjust. IF it still grinds after adjusting too tight, then something might be wrong with the clutch. Was that replaced recently?

Try over adjusting it first and let things settle in for a thousand miles or so, then readjust.

When it's up on jacks, do the rear wheels turn with the tranny in gear, with the clutch pedal pressed down?

I'd try this. The symptoms kind of sound like the synchros are putting in some effort 1-5 but without complete disengagement you're going to grind going into reverse.

If the car sat for a while maybe the pedal board itself is warped, and you're not able to depress the clutch enough. The rubber stopper on the board is adjustable.

Wait wait...I just noticed the P.S. in the first post. After disengaging the clutch and letting off the pedal you lose the 1mm gap at the adjustment screw? Did you disassemble the arms from the shaft? Maybe all that time things have seized up some there?

[TargaWoods]

Originally Posted by PeteKz

You may have adjusted the clutch cable "correctly," but I've had similar issues on cars in the past. Try adjusting the cable until you have no free play. See if it grinds going into reverse. If it doesn't, then back off the adjustment until you barely don't get grinding. Over time, the clutch wears and the "engagement zone" tightens up, and then you can readjust. IF it still grinds after adjusting too tight, then something might be wrong with the clutch. Was that replaced recently?

Try over adjusting it first and let things settle in for a thousand miles or so, then readjust.

When it's up on jacks, do the rear wheels turn with the tranny in gear, with the clutch pedal pressed down?

There’s no free play currently. You suggest loosening it then??

The wheels do spin with tranny in gear and clutch pressed down.

[TargaWoods]

Originally Posted by David Inc.

I'd try this. The symptoms kind of sound like the synchros are putting in some effort 1-5 but without complete disengagement you're going to grind going into reverse.

If the car sat for a while maybe the pedal board itself is warped, and you're not able to depress the clutch enough. The rubber stopper on the board is adjustable.

Wait wait...I just noticed the P.S. in the first post. After disengaging the clutch and letting off the pedal you lose the 1mm gap at the adjustment screw? Did you disassemble the arms from the shaft? Maybe all that time things have seized up some there?

Pedal board is straight, I moved the stopper back to ensure the 25mm lever travel

Yes, the 1mm closes after pressing the pedal. No disassembly on arms from shaft. I’ve hit it with PB Blaster, but that’s the most cleaning/disassembly it’s gotten.

I talked with a local mechanic.
He said if the car goes happily in gear on 1-5, but refuses reverse, he said try changing the trans fluid and seeing if starting in gear in reverse and also driving and switching gears will warm up and wake up the reverse gear because something could be bound.)

[icarp]

pull the e brake up , put it in 3rd , then reverse , there should be no grind
ian

[TargaWoods]

Originally Posted by icarp

pull the e brake up , put it in 3rd , then reverse , there should be no grind
ian

What’s your hypothesis for what might be wrong? I’ll try it, but shouldn’t 3>N>R be the same as going 1>N>R

[icarp]

the wheel spin is the problem, they have to be stopped , ebrake or on ground
3rd slows the shafts better

[David Inc.]

Originally Posted by TargaWoods

Pedal board is straight, I moved the stopper back to ensure the 25mm lever travel

Yes, the 1mm closes after pressing the pedal. No disassembly on arms from shaft. I’ve hit it with PB Blaster, but that’s the most cleaning/disassembly it’s gotten.

I talked with a local mechanic.
He said if the car goes happily in gear on 1-5, but refuses reverse, he said try changing the trans fluid and seeing if starting in gear in reverse and also driving and switching gears will warm up and wake up the reverse gear because something could be bound.)

I don't know if it's the problem but it's definitely a problem that will cause binding. I recall my 915 would grind and stick a lot more during shifting when my helper arm and main arm were frozen together. It was an absolute nightmare to pull apart; I don't remember exactly how it happened but I recall using plenty of heat and a Dremel.

Mine were completely frozen together, and maybe yours are just binding, so fingers crossed it's not as bad. Maybe if you disassemble it, clean up the shaft and arms then reassemble with lube you might see an improvement. Again, it might not be the problem but it definitely shouldn't do that.

[walt]

Your adjustment procedure doesn't sound like the one I have used in the past. Have someone step on the clutch and from underneath the car measure the distance the clutch cable lock nut moves. Should be .98in +/- .02. Maybe you just don't have full engagement. That 1 mm gap disappearing is pointing you to the problem.