1993 NH 2120 (the best), 1974 MF 135 (sold, but solid), 1947 Farmall A (bought, sold, bought back, sold again), 1956 MH50 lbt (sold, in 1980, darn it)
This is often binding where the linkage enters the transmission case. Lube and operate with PB Blaster or other penetrant. I assume you try to engage after slightly moving the tractor in gear?
Jim
Still need help. The linkage that is accessible moves freely when disconnected from the arm that goes into the transfer case. That black lever that enters the transfer case seems to be bound up. Is that possible?