It is worth fixing. Without the power shift it will not shift or move. Could be anything from a clogged filter or valve adjustment to a complete overhaul. Been a while since I've had to do anything with one. Does it not shift into a certain gear? Range? Or is there is consistent problem with all of the gears. I would start with a fluid level check and quality check. If it's very low or burnt it may be a problem. If it's okay it may just be a matter of changing the filters and oil. Basically there are 4 clutch packs in the trans. C1, C2, C3, and C4. 4 ranges basically. Also has a high and low. Pretty bullet proof with regular maintenance. My uncle bought 3 new, still going strong, but with anything it is only as good as the operator and maintenance it gets.