1960 GMC C1000 Clutch slave piston excursion issue. Stock 3 on the tree.

[garrstim]

I replaced the dual master brake/clutch assembly and the clutch slave cylinder in my 1960 305A C1000. I carefully bench bled master before installation. I rigorously bled everything using MitiVac after installation.

Now I've discovered that the slave piston excursion seems to be only about 60-70% of full linear travel toward the snap ring at the mouth of the slave cyl with the clutch pedal to floor. I think that travel should be really close to, or all the way to snap ring with full depression of the clutch pedal. Is this a correct assumption? The master piston properly rests against its snap ring when the pedal is not depressed.

As a result of the above, the clutch does not now fully disengage like it previously did. With the engine running, there is a gear clash when attempting reverse engagement (cannot engage, and do not enjoy) and rather reluctant 1st, 2nd, and 3rd engagement as evidenced by somewhat difficult shift requiring more force at shift lever than previously experienced. Probably synchros complaining. With the engine OFF shifting is easy and positive, as normal.

The central question involves the slave piston travel. Any answers from somebody who has suffered a similar fate???

Could some patient soul among you take a look at their 1960 system by pulling back the rubber on the slave and peering into the bore as a helper depresses the pedal to the floor? You can easily see the piston with the rubber slid away.

I'm led to believe that bleeding the clutch slave can be very frustrating, but I was fairly confident that I bled fully...

Thanks you guys for your comments and advice.
Barry

[AZKen]

Bleed slave on the truck and adjust it's push rod per shop manual. Then see how it works and report. See marketplace for a 1960 Manual if you don't have one.

[Funky61]

Here is a link with a tip on bleeding the slave cylinder and the adjustment

http://67-72chevytrucks.com/vboard/s...inder+bleeding

[Jim A]

I went through a similar problem a short while ago.
I'm not sure what differences there are between your 1000 and my 1500 (four speed).
My whole problem began with a gradual loss of full disengagement over a couple of years.
It turned out that the throwout bearing had failed and ate up the release fingers on the pressure plate.
After a tough rebuild process, I got things in order but had trouble finding the balance between full disengagement and enough clearance to allow the new throwout bearing's not being always in constant contact and turning.
I think it is helpful to look at the master cylinder and slave cylinders as a teeter-totter.
The master needs to travel its full distance to make the slave do the same.
Removing all the air (bleeding) is necessary but easy.
What I found was that the pedal linkage was not giving the master piston full range.
I do not know why. Some modification fixed it and (fingers crossed) I have had flawless clutch operation during this hay season, for the first time in a long while.
I have had the truck for 52 years, done all work needed myself and am really glad to have it working right.
More details are available if you thin they might help.

[Jim A]

garrstim: Was my input useful? More details needed?