Not enough clutch cable travel

Mr Project · 03-12-2015, 05:05 AM

tl;dr - I replaced the clutch cable, floorboards, pedal stops, and rebuilt the pedal cluster, but cannot get 25mm of clutch cable travel. I'm 'peaking out' at a little over 22mm.

A little background for the problem: The car is my '82 911 SC. It has a 3.2l Motronic engine but the original SC 915 gearbox.

I rebuilt the engine a year or two ago and adjusted the clutch linkage when re-installing everything. The disc, flywheel, pressure plate, etc all looked fine and worked fine. The 1-2 shift has never been great on this car, but it was disengaging properly and working fine overall. I did not have a helper available, so I didn't verify the total cable travel. I did the 1.2mm/1.0mm adjustment and since it worked I didn't check the travel

Early this year, I pulled the car out on a couple of unseasonably warm winter days and drove it - it started out fine but after 100 miles or so, I was having tremendous difficulty shifting. It was clear that the clutch was not fully disengaging. If I force the clutch pedal down as far as i could, it got a little better - enough to limp it home.

I re-adjusted the clutch linkages and drove it around the block. Problem solved! It shifted fine again. However, after running errands around town for 15-20 miles, as I pulled into the driveway I felt something 'shift' in the clutch pedal/linkage and it was not fully disengaging again.

At this point I visually inspected everything and it looked OK, but the clutch cable was obviously worn and I thought it made sense to just replace it. So I replaced the clutch cable and the little attachment parts at the pedal cluster end. After doing so, I could not get 25mm of cable travel, no matter what I did with the adjustments.

Thinking that it might be pedal cluster related, I rebuilt it with bronze bushings. Everything actually looked basically fine, but I did it anyway, and reassembled everything. I'm still stuck with a max of a little over 22mm of travel.

I'm stumped. Help!

New ABS floorboard and clutch pedal stop

Clutch pedal stop adjusted to max travel

Rebuilt cluster with new bushings and new clutch pivot pin/attachment. All nice and tight.

New cable and 1.2mm/1.0mm adjustment completed

Zero the measurement at 'rest'

Max travel with clutch pedal against stop

wolds · wolds's Garage

I had a similar issue after I replaced my clutch cable. There are threads on our site that have pointed out that some of the replacement cables were manufactured longer than stock. That said, for my application I needed to remove about 10mm of the threaded end of the cable so that the clevis could be spun father down the cable. This resolved my issue. I can also tell you that it is necessary to cut the end off because if you don't there is a good chance that the end of the cable will bind on the arm that the clevis attaches to. I would also suggest that the pedal stop on your floorboard be adjusted to its closest position to the pedal so that as the cable streches you will have some adjustment left.

Mr Project · 03-12-2015, 06:51 AM

Good thoughts, thanks. I had seen some of those threads but I thought if I could get already enough cable tension for the 1.0mm adjustment, then shortening the clevis end of the cable would not change the overall travel, right?

My thought was that all that shortening the cable would accomplish is making sure that I could get the tension within a reasonable adjuster range at both the clevis end and the transmission bracket end of the cable. But maybe I'm all wet - my way is not working so far!

wolds · wolds's Garage

The overall travel is determined by the pedal stop which is why I suggested that you do the initial setup with the stop closest to the pedal. That way you have the ability to make up for cable stretch.

wolds · wolds's Garage

Just looked at your picture of the pedal cluster rebuild and can tell by looking at the picture that has the clutch cable clevis in it that you need to spin in farther down. Mine is about as short as you can get it and still use the jamb nut which I'm not sure what purpose it serves.

Mr Project · 03-12-2015, 11:18 AM

I totally agree that I'd prefer to have the pedal stop set 'short' to allow for cable stretch. I just don't understand mechanically how shortening the clevis point will alter the total travel (I'll just have to lengthen it at the transmission to get the same tension), but I'll try it!

wolds · wolds's Garage

I wish I could come up with a better explanation for you, maybe someone else can give you a better analogy. I can also tell you that as you make changes to the clevis at the front it affects the adjustment at the transmission and you should start the process by making sure the cable is slack by backing off the rear adjustment. If you don't do that you will find it impossible to get the clevis attached at the front arm once you shorten the overall cable length.

mreid · 03-12-2015, 02:57 PM

The pedal stop adjusts the throw. You adjust it to achieve the correct clutch disengagement.

wolds · wolds's Garage

Ya, what he said. You take up the slack in the cable and draw that free play down from 1.2 to 1.0mm on the SC's at the trans.

Quote:

Originally Posted by mreid

The pedal stop adjusts the throw. You adjust it to achieve the correct clutch disengagement.

Mr Project · 03-13-2015, 04:55 AM

Thanks guys. I do understand that, my problem was that I didn't have enough adjustment available at the pedal stop to allow for 25mm of travel.

So last night, I took wolds advice and tightened up the clevis side of the cable and then re-adjusted at the transmission bracket. As I expected, once I had the 1.0mm cable tension set correctly again, the total travel was the same 22.x mm.

I went through the plastic ABS floorboard carefully, and compared it to the remnants of my original plywood floorboard. I was hoping that perhaps the holes in the ABS floorboard were not allowing as much clutch stop adjustment as the original pieces. Not so...the ABS piece is well-made and a very good match for original.

However, it was the only thing I could think of to allow for more travel, so I expanded the clutch stop mounting holes in the ABS floorboard slightly to allow for more adjustment of the stop.

After some monkeying around with this, I got to 24.5mm of travel. I called this close enough and put the car on the ground to road test it.

That's when things went sideways. I could not get the car in gear at idle. It was clearly not disengaging the clutch. I could shut the car off, put it in gear, depress the clutch, and start it, but it was clearly still dragging the clutch slightly. After experimenting gently, the car started making horrible noises (scraping, grinding, rotational noises).

I'm fairly certain that my real problem is inside the bell housing. My pressure plate/throwout bearing is highly suspect. Sigh. Out comes the drivetrain!

mreid · 03-13-2015, 05:18 AM

Sorry to hear that! I've pulled my engine so many times that draining the oil is now that longest part.

Mr Project · 03-13-2015, 05:31 AM

Yeah, the only real downside is that I have another car stuck on the lift right now, so it has to wait in line! The weather has just turned nice this week after a long winter, so I'm antsy.

kodioneill · kodioneill's Garage

Sounds like a failing t/o bearing fork.

john walker's workshop · 03-13-2015, 05:40 AM

Probably broke the release fork. They develop a crack, which gradually enlarges.

wolds · wolds's Garage

You wanted to inspect your clutch anyway right

Sorry to hear that the project has snowballed on you.

theiceman · 03-13-2015, 07:00 AM

well i guess i should have read the first post first

. i think in hind sight now i understand .. you dont have the throw not because of the pedal stop . but because it is not going back far enough to its original position due to something busted and jamming in the bell housing ..

john walker's workshop · 03-13-2015, 07:26 AM

Probably not the issue, due to the bellhousing noise, but the pedal can bend at it's horizontal part. If you see a slight twist there, it's bent.

Jeff NJ · 03-13-2015, 08:39 AM

I had the same issue as you, along with serious trouble getting it into reverse when the car was warm. I tried everything outside the trans - cable, pedal cluster, omega spring, you name it, to no avail. I pulled my motor in January and this is what I found:

So part of the friction disc broke off and was jammed between the friction disc and the pressure plate or flywheel (don't remember which side of the friction disc) . Rivets were floating around in there too. This prevented the clutch from disengaging completely (hence the reverse grinding) and the clutch throw was restricted from going the proper 25.5 +/- throw. The release fork is fine.
I haven't put it all back together yet, so I can't promise my throw will be normal when I'm done, but I think it is time for you to pull the clutch and check it out.

Taxi! · 03-13-2015, 02:39 PM

Quote:

Originally Posted by Mr Project

Thanks guys. I do understand that, my problem was that I didn't have enough adjustment available at the pedal stop to allow for 25mm of travel.

So last night, I took wolds advice and tightened up the clevis side of the cable and then re-adjusted at the transmission bracket. As I expected, once I had the 1.0mm cable tension set correctly again, the total travel was the same 22.x mm.

I went through the plastic ABS floorboard carefully, and compared it to the remnants of my original plywood floorboard. I was hoping that perhaps the holes in the ABS floorboard were not allowing as much clutch stop adjustment as the original pieces. Not so...the ABS piece is well-made and a very good match for original.

However, it was the only thing I could think of to allow for more travel, so I expanded the clutch stop mounting holes in the ABS floorboard slightly to allow for more adjustment of the stop.

After some monkeying around with this, I got to 24.5mm of travel. I called this close enough and put the car on the ground to road test it.

That's when things went sideways. I could not get the car in gear at idle. It was clearly not disengaging the clutch. I could shut the car off, put it in gear, depress the clutch, and start it, but it was clearly still dragging the clutch slightly. After experimenting gently, the car started making horrible noises (scraping, grinding, rotational noises).

I'm fairly certain that my real problem is inside the bell housing. My pressure plate/throwout bearing is highly suspect. Sigh. Out comes the drivetrain!

I'm not sure what's causing the noises you're experiencing, but I had the same problem with my clutch adjustment recently and eventually attributed it to the aftermarket floorboards (and clutch pedal stop) that I changed with the clutch cable and springs. It just didn't seat the same as the OEM part.

DRACO A5OG · DRACO A5OG's Garage

Re: Cable. Did you make sure the cable's rubber shield is seated in the port of the tunnel all the way. I recall the shield after the bowden may come loose and plop out of the port. just a brain fart

Suspect TOB, no need to drop it. Remove the wheel, reach in and put your finger inside the inspection port and feel for the fork is properly on the TOB channel. If not in properly, time to drop her.

Don't worry it is faster the second time around and you will see items you may have missed