what can cause the shuttle shift lever to pop out of forward or reverse when moving on a 1967 580ck? mechanical transmission
I would first check the linkage to make sure it is in a detent position when in F or R. The detent slot on the shaft could be worn, spring broken holding tension on the detent ball, the gears may have taper causing it to have pressure against the detent forcing it out. Also end play in the shafts just enough to have a end thrust forcing it out of detent. You should be able to unhook the linkage from the F/R lever and feel the detent as you move the trans case lever, should have some stiffness in and out of detent. Always block your wheels for safety while doing this.