86 K10 clutch not disengaging

[Catrik]

'86 K10, 6.2D with SM465.

The clutch wont always disengange completely. Sometimes it works perfect. Sometimes horribly and sometiles less horribly.
Thought I might had a leak so I took both clutch cylinders, the hyd. line between them and the reservoir out. I checked and everything looked fine, cylinder bores/seals etc.

I put everything together on the table, I put the slave cylinder with the rod on vise (so the cylinder wont move), put fluids in, air out.
The pushed the master cylinder hard with a tool and I dont  see any leaks.


I didnt have any problems before but it's been getting worse. Usually, when I start the truck, first shift goes perfect. After that it wont disengage the clutch completely.
I was sure it was a leak in the hydraulics but I didnt even try replacing any seals because they looked like new (+I didnt find any leaks).

Any ideas? How much should I have travel on the slave cylinder? And how long should the slave cylinder rod be?

[roundhouse]

I'd replace both cylinders.  They may have an internal leak that jut causes a loss of pressure but doesn't leak fluid to the outside

[Engineer]

I'd replace both cylinders.  They may have an internal leak that jut causes a loss of pressure but doesn't leak fluid to the outside

This^^

[VileZambonie]

Clutch pedal travel should be approximately 8.3 inches, and slave cylinder rod should have a minimum of 1 inch travel, measured at the clutch fork.

[Catrik]

How long should the slave cylinder rod be? I think they are supposed to be fixed lenght but mine is adjustable. I will check the pedal&cylinder travel tomorrow

[Catrik]

I replaced both cylinders and the hose between them. Dorman part numbers CM39732 and CS37791 for the cylinders. Eyeballing they seemed to be the same, new master cylinder was slightly thicker but I figured it was because its cast metal unlike the old one. Replaced them, went in without big issues and here's how its now:

-clutch pedal is noticeably heavier now
-feels like I got all the air out
-some problem with the switch that wont let the car start if clutch isnt pressed.
It's missing about 5mm from the travel, I put a zip tie on there to fix it for now.
Wasn't able to see what the problem is there (new part had longer rod and cylinder bottoms out? Did I bend the switch bracket?)
-aaand it still will not disengage completely.

It is better now, the clutch really starts grabbing about half way on the the pedal travel (like it should be), but it still drags too much when pedal is completely down. Cant get  any gear in without force.

It's so freaking hot outside that I wont be doing anything till evening but let me know if you have any ideas. Biggest confusion is why the pedal is so stiff now and what happened to the switch??

[Catrik]

I tried airing some more but there dont seem to be any air left. Also checked the pedal, if I remove the master cylinder rod pedal goes all the way so I'm guessing the master cylinder bottoms out. What the heck could be the problem?? Must be something in the clutch or pressure plate or something?? Ideas?

[Catrik]

Finally had time to take a closer look at the clutch. I found only one clear issue, the release bearing was installed incorrectly (spring tabs outside the bearing groove). How ever, despite what I read online, I dont understand how this could cause clutch drag? I'd think that when I press the clutch pedal, the spring tabs would just bend away and the bearing would press the pressure plate as much as it would when installed correctly?
The release bearing is 31mm (1.21") overall lenght, should be correct?

Other thing could be transmission input gear dragging. The pilot bearing felt ok (from what I read, Im going to replace it with a bushing).
Maybe bellhousing misalingment? About a year ago, I noticed one bellhousing bolt was about to fall off. I checked all bolts I could see and a few others were a bit loose too. I cant say for sure but it might have been about that time when the clutch got worse (AFTER retorquing the bolts). After that the clutch dragging was kinda on/off, sometimes works sometimes dont. Until now it was just never releasing completely.
Now there was one bolt missing on the bellhousing, others were tight~ish. I will have to check if the bellhousing is warped, any more ideas other than that?




EDIT: Works now. Installed a complete clutch kit. Most likely the pressure plate had gone bad.


Also, I opened up the SM465. The coating on the shift forks is starting to come off. There was a little wear on the gears (1-2 and 3-4 hubs?) that the collar thing slides on. Everything else looked okay. See photos here https://www.dropbox.com/sh/jnbhis3kn3pgs6y/AADDQnUUJGBZGEHXo4dDp1Mra?dl=0

I drive only about 3000-5000 miles a year so I though to just put them back in. Should be OK for many years, yes?