the two speed itself does work then? i guess for pm, if it doesnt howl and shifts ok. you could replace the pinion seal, but i wouldnt if it isnt leaking, and maybe the wheel seals, but there again if they arent leaking. You could change the gear lube if ya want. If its workin ,as the old adage goes dont fix it...???? if the two speed isnt working or shifting, its probably the rubber diaphram on the rear end. easiest way to check that is pull both vaccum lines, and pull vacuum on it and see if either side leaks.... can even just suck on it. to make it shift or move though would take probably a little more than ya can suck....
if its the shifter mechanism on the frame thats run from a cable, you can usually i think just clean those up and replace o rings i think, dont remember rebuilding one for sure...
