My '93 has 110k miles. It is getting increasingly hard to put in 1st gear and is popping out of gear occasionally during takeoff. There is an aweful shudder through the whole truck when this happens :-( It's also getting hard to put into 3rd gear unless the engine is over 2500 rpm.

Does this sound like a clutch issue or something else? I think it had a new clutch at 75k miles but am not sure; I'll have to ask the 1st owner (my sister-in-law) about that.