1988 f-250 4x4 used for snowplowing. Replaced clutch last fall when the slave cylinder went out, replaced master and slave at the same time, the only old part in the whole system is the hose maybe. it ran fine a couple days ago, and yesterday i got into it and it's slipping in second, and every gear above, i've bled the system again, finding no air, and it still slips. i'm loathe to call it a bad clutch it's a heavy duty unit that the clutch guy said would be perfect for plowing, it's not got a whole lot of miles on it, and about 100 or so hours plowing. is there something in the system that might cause it to be partially disengaged? a couple years previous i adjusted the piece that connects to the linkage as the Haynes says to, pull it off the end of the shaft and set it where you want it and pull it back in with the nut, forcing it to sit in the new spot, i thought it might have slipped back, but that would make the clutch sit too low in the pedal, as it is it's almost at the top of the pedal. i'm lost and don't want to pull this transmission again, everything'a almost new! it just seems to be slightly engaged at all times

 

or disengaged, i'm not sure the terminology, it doesn't seem to have a firm grip on the flywheel.

 

You need to ensure that you have around 11/2 inches of free play at the pedal. Adjust the linkage as necessary.

 

no adjustments to be made, it's a hydraulic clutch

 

I thought from your post that you had an adjustable push rod, guess not.
Then try opening the bleed screw. If fluid spurts out, the line between the two cyls may be restricted. If fluid only dribbles out then it may be that the clutch disc is worn.

 

Where'd ya buy that slave?

Sounds like ya got a defective one, not adjusting to wear as it should (no you shouldn't have that much wear yet, did you replace or resurface the flywheel?) or its hanging up on itself rather then smoothly sliding in and out.

Make up a quick gauge and measure the bearings total travel from pedal all the way up to all the way down, if not equal to or exceed spec would suggest it not fully relaxing, withdrawing far as it should pedal up. Not fully disengaging being the opposite problem as it pertains to total bearing travel distance, you have the opposite problem.

Measure it, should move 0.53inch Minimum.

As with Lazy K not sure I follow ya on your previous adjustment made IE; i adjusted the piece that connects to the linkage as the Haynes says to, pull it off the end of the shaft and set it where you want it and pull it back in with the nut, forcing it to sit in the new spot, gotta say reading that sounds like you adjusted the neutral safety switch? but as stated not sure I follow that exactly.

Look at the rod between pedal and clutch master, some are adjustable for lenght. If yours is you might simply need shorten it little bit.

If that will work first sign will be doing as Lazy K suggests, loosen bleeder release pressure. Clutch might not slip first couple attempts, least not until cycled pedal up/down/up couple times again.
Test drive "speed" shift after taking off from stand still in first gear, shift to second and third without using clutch see if clutch slips. If it doesn't that will be some useful info how proceed next.

 

get this mice had built a nest in the bellhousing, and got all their nestbuilding materials in the "flex plate?" or pressure plate, anyway, there was nestbuilding supplies all around the fingers of the clutch not letting the fingers come all the way back up, so therefore slipping, pushed the pedal in, and ran a rod between there to fish out all the debris and WALAH! it grips great!

 

Oh that's good, hate see it when guys gotta tear one all apart again because of some china part, not the issue here at least.

Stopping them fingers from coming back, that is one tightly packed mouse nest!