My tranmission would not shift into any gear yesterday except 4th unless the engine was shut off it done this for about 15 min and then after I got it up to speed it was fine. The clutch master cylinder was full .

I have been having some clutch slippage issues but only when running with a fully loaded trailer up hill tring to exelerate.

any help would be appericated

 

Is there any noise when you push clutch pedal down? Maybe pilot bearing or release bearing are gone.

 

no noise if I let it off the floor about 1/4 in it helps a little

 

May also want to check the transmission oil level, and check for any sign of abnormal wear in the oil. Robert may also be onto something. How many miles are on your truck? Does it still have the dreaded dual mass(crap) flywheel? If it was mine I would pull the transmission and clutch, then investigate things.