clutch adjustment

[Bill Romano]

I now buy nearly everything you've said. I typed it up and pasted it into my WSM should anyone who inherits it need to adjust or change the clutch. Here's what I said. Editorial comments are welcome.

Clutch Release Adjustments
The following two adjustments must be coordinated. The result will provide the correct adjustment for both release bearing and clutch pedal free play.

Adjust Clutch Release Bearing
Even if the clutch release bearing (aka the throw-out bearing of simply TO) has never been removed, it should be checked. This is done by disconnecting the clutch pedal return spring, removing bearing, checking for smoothness of operation (and replacing if necessary), lubricating lever slots for bearing with graphite grease and reinstalling.
The WSM provided confusing instructions but ended with a need to set the TO bearing face 50 mm short of transmission-engine surface.
After thorough investigation including input from the 356 Registry’s talk forum, the only way to get the 50 mm distance is to tighten the adjustment of the clutch cable length (at either end) so application of force on the clutch lever occurs immediately as you start to push the clutch pedal (i.e., there is no slop in the clutch cable). “Free play” is basically the distance the bearing moves before contacting the clutch’s spring disk.

If adjusting at pedal end, you may need to hold the threaded end of the cable with pliers.
At the clevis end, do not tighten past the end of the threads where it will bind with the clutch lever. Secure the clevis in the clutch lever by inserting the clevis pin and locking it with the spring clip.

You may need to adjust the Bowden tube at the fitting on the transmission to increase the amount of cable appearing at the pedal end to achieve necessary adjustability. Clue: there aren’t any threads in the bracket bolted to the transmission … to move clutch cable from the transmission end to the pedal end you loosen the Nyloc nut (19 mm ATF) while holding the Bowden tube nut (17 mm ATF). The threaded end of the Bowden tube should slide rearward in the bracket. And the cable that disappears into the Bowden tube should show up at the pedal end. You need to leave a minimum of three threads of the Bowden tube exposed engine side of bracket to secure bellows.

When the engine with clutch is ready for installation, measure the distance from the TO bearing contact area of the spring disk to the engine-transmission mating surface. This should be 1 mm less than the measurement of the face of the TO bearing to the mating surface of the transmission. Adjustments are made by changing the length of the clutch cable.

Secure the clevis and pedal adjustment by tightening the lock nuts. Grease the adjustment threads to prevent rust.

Adjust Clutch Pedal Stop
With the engine running, pump the clutch pedal several times and check the free travel. Now you should be able to feel free movement of 20-25 mm before the TO bearing begins to push the spring disk of the clutch. If you don’t feel any free play, you will need to adjust the cable length.
Loosen the two 6mm bolts securing the stop plate. The stop should be positioned so that you can just engage reverse without crunching. I added a strip of a plastic ruler in mm to the left edge of the peddle stop to provide some way to record the set position. The peddle stop has a rubber coating on the back side so the locating ruler should be on the other side.

[Martin Benade]

Very good! One thing not mentioned is that the bowdon tube must have a dip in it, that allows the transmission to move in response to torque without affecting the cable pull. Otherwise the clutch can chatter very nicely.

[Jon Bunin]

And if you continue to have difficulty, you might need to confirm that all components involved are correct for your car, and are properly installed.

[Tom Tate]

I have to chime in here as I just returned from the Lancaster Drive put together by Cliff and Jean Murray (great weekend BTW) and struggled with a chattering clutch for 700 miles down and back from Boston. This is the '57 T1 coupe that broke a clutch cable at the Catskill Drive last year. After replacing the cable in the parking lot of the event I had it tight enough to work but wasn't happy with the pickup point. It didn't get on the Winter Project list so the week before leaving I just tightened the cable at the pedal and rolled out of town. Shifting was not a problem but starting off was real tricky. It would chatter bad in first and starting up hill was a real test. Starting down hill was better, no chatter. A close friend (thanks George) said the I needed to adjust the Bowden Tube to make sure that it wasn't straight but had a bit of a curve to it. There was still too much slack in the cable anyway so I backed out the Tube and it fixed the problem. So to clarify since the Factory repair manual doesn't say much about it, here's the story:
The Bowden Tube end nearest the transmission goes thru an unthreaded bracket that is mounted to the drivers side of the transmission. There is a self locking 19mm nut that determines how far the tube goes into the bracket. That 19mm nut is mounted on the threaded portion of the tube before it goes into the bracket. The tube itself has a 17mm end on it that makes it easy to hold while the nut is moved on the threaded end of the Bowden Tube. The further the tube goes into the bracket the straighter the cable it holds becomes. So as you run the 19mm nut towards the end of the tube (towards the back of the car) it effectively shortens the cable by making the Bowden Tube bend (cable inside has to travel a greater distance).
In my case, moving the Bowden Tube out of the bracket about 3/4" solved all my clutch problems. It put the pickup where I wanted it (about 1 1/2" off the floor) and most important, stopped all the chatter.
I can't believe that I have crawled under these cars all these years and didn't know the importance of how that Tube effected the clutch operation. If I knew how easy the fix was I would probably have stopped on the GW Bridge and fixed it on Sunday.
KTF

[David Jones]

I believe I know that because I read it in a manual decades ago. Not sure if it was factory or after market.

[Jon Bunin]

...So to clarify since the Factory repair manual doesn't say much about it, here's the story: The Bowden Tube end nearest the transmission goes thru an unthreaded bracket that is mounted to the drivers side of the transmission. There is a self locking 19mm nut that determines how far the tube goes into the bracket. That 19mm nut is mounted on the threaded portion of the tube before it goes into the bracket. The tube itself has a 17mm end on it that makes it easy to hold while the nut is moved on the threaded end of the Bowden Tube. The further the tube goes into the bracket the straighter the cable it holds becomes. So as you run the 19mm nut towards the end of the tube (towards the back of the car) it effectively shortens the cable by making the Bowden Tube bend (cable inside has to travel a greater distance). In my case, moving the Bowden Tube out of the bracket about 3/4" solved all my clutch problems...

Tom, I'm glad that you solved your '57 A clutch problems, but the basic adjustment of the bowden tube is described in the B and B/C factory manuals, and wasn't an issue in this thread.
The original factory A manual doesn't describe this, because the adjustable bowden tube didn't exist when the manual was printed.

You shouldn't have to deviate much beyond the basic adjustment , "...so that at least three threads on which the rubber dust cap can be mounted protrude from the bracket..." (below).
If you have to, then I'd suspect there are issues with the parts involved, such as not being correct for the car, or issues with their installation, or other issues with the clutch, the engine or the car itself.

[Tom Tate]

Thanks Jon, I did look at the exact page that you shared and saw the exact same mention of the dust cover and no other information, hence my lengthy post. I hope it is helpful to others as are your comments.

[Martin Benade]

The A had the tube adjusted with washers like a VW?

[Jon Bunin]

The A had the tube adjusted with washers like a VW?

Martin, the early A and pre-A manuals refer to a clutch cable "adjusting sleeve at the end of the chassis".

I hope it is helpful to others as are your comments.

Tom, it will certainly be helpful to others.

Your 3/4" adjustment equates to 12.7 threads, quite a lot. The bracket supporting the cable is only 7/8" long.
If the manual says "...so at least three threads...protrude from the bracket...", where did your final adjustment end up?

[Tom Tate]

Jon, without going back to measure it I'd say that there is now at least 1/2" of threaded Bowden Tube protruding past the back of the bracket. When I got under there to look at it the self locking nut was not even contacting the back of the bracket. Clearly I threw it back together last year in NY without thinking about the importance of the compression on the Bowden Tube. Works great now as intended. KTF

[Thom Fitzpatrick]

This is a timely thread, as I just installed a new cable.

What is the significance of making the clutch cable adjustment at the front vs at the back? Seems like trying to make any regular adjustment at the front would be a major PITA

[Martin Benade]

I must be really tough. I’ve often heard that people dislike adjusting the cable at the front. I’ve always thought that was the easiest place to do it.

[Harlan Halsey]

+1
But then I have a cheap vice grip with the jaws channeled so that they grip the cable without damaging it.