Clutch Issues (need help)

Hello, I have a 1993 B2200, it has 136,kkk miles on it. I replaced the master clutch cylinder and the slave cylinder because one day it all went out and my clutch pedal hit the floor. Anyway, I got all of that replaced and bled out. Everything seems to be working fine but now my clutch is slipping? One day the clutch wont slip at all and then other days the pickup has a hard time going. It seems to get worse once I have been driving for 20 minutes or more?. I have never had a clutch go out before, is this a common way for a clutch to go out or is there another issue?.
I believe this is the original clutch, so it's no surprise if it is going bad.
I always thought once a clutch starts slipping it doesn't stop?.

If the clutch is going out, what all should I replace once I'm in there?, I know I should replace the throw out bearing anyone have any other ideas???

Thanks for any help

I've never heard of a worn out clutch that still works sometimes. It sounds like wear in the slave causing the piston to hang.

That's what I thought was odd, why does it slip one time and not the next?
I just replaced the slave and master cylinder. Would a air bubble cause this?

Check for swelling on the rubber line from the master to the slave. They can swell shut which would allow you to put pressure in when you push the pedal but not let the pressure off. I've seen this on motor cycle brake lines which will lock the caliper. You can test this by pumping up the pedal and then climbing under the truck and cracking loose the slave bleeder and see if the pushrod moves. It might just be cheaper in the long run to replace the line and be done with that as a 23 year old possibility.

Actually, on the B2200 there are TWO flexible clutch lines. I have had my '88 for 22 years, and have replaced both. I've also replaced both clutch master and clutch slave several times.

My clutch began slipping at maybe 150K, had a shop install a complete Luk kit, in about 2005. This included resurfacing the flywheel surface, new pressure plate, new disc, new release bearing, and new pilot bearing. Still works fine, at 212K.

My 1998 Frontier has had an Exedy clutch kit installed in it, also works fine (213K).

Thanks for the help, I bet that line is my problem, I will get one ordered and installed ASAP.
Thanks again and I hope everyone has a wonderful Holiday!

My 1987 B2600 did the same thing after about 20 min then the NEW clutch would slip
I replaced the master cylinder and it quit, seem's these master cylinders
have a weird control valve in them that will build up pressure.I'm on my 3rd.
Good luck
BSDAN