[Kurt in NJ]

If you can put it in firsty---then drive, stop put in rev then move in rev most likely it is not the clutch

There is a interlock in the shifter, perhaps your shifter lever ball and the forks are worn--can you shift 2-3 with engine shut off? ---a common problem with worn shifter is that going from 1-2 that #1-rev shifter rail isn't in the neutral positiion, but the lever ball/fork groove wear allows the shifter to go to the 2/3 rail without fully being in r-1 rail neutral----try finding the r-1 neutral detent and then go across the "H" to 2-3 rail, ----follow the exact "H" patterrn, not just push the lever towars 2nd

it's also possible that a detent spring broke or debris got into the shifter rail and is jamming operation ---