My 93' c1500 4.3L manual has a funny squeak. I hear it only at low speed when I let off of the clutch pedal and give the engine gas to accelerate. It increases with the speed of the truck not the RPM of the engine. It goes away if I push in the clutch pedal. If I release the pedal it comes back again. I recently replaced the clutch on this truck and I didn't start hearing the squeeking untill 2-3 months after the replacement. Any ideas?

My first thought would be the U-joints

UPDATE: I put the rear end up on jack stands, started the truck and put it into gear. No squeak. I gave it some gas, no squeak. Also, there seems to be no squeak in reverse. Thanks for the help.

My first thought would be the U-joints

I agree. U-Joints under a load would be the 1st suspect. Even though they may feel tight.