I have a 1966 K20, it was on the tree but the farmer i bought it off of put in a 4 speed on the floor. I believe its a muncie, but im not certain. I ordered a rebuild kit that covered multiple makes and models. I matched new parts with old when i reassembled. My question is, when I start the truck my drive shaft is spinning in neutral and when I have the clutch pushed in. (the whole truck is on blocks right now). I also cannot put it in 4th gear. What should be my best course of action?
Sounds like a clutch issue if the driveshaft is spinning with the clutch pushed in. New clutch? I ask because I bought a new replacement clutch once for a '70 Nova and it was made wrong at the factory. When I took it back we compared it with another new clutch and you could visually see the distance from where the throwout bearing contacted the clutch was different between the two. The 2nd clutch worked just fine. Did you hand turn the input shaft and shift it through the gears when you rebuilt it? It is possible to have some parasitic drag that could spin the driveshaft when the transmission is in neutral (with the clutch engaged) but there shouldn't be enough torque to move the vehicle.
