My recently converted axle shifts great. Originally a single speed axle, I acquired a 2-speed pig from one of our members, his doner is a 1956 2 ton, mine is a 1957 2 ton, both GM corporate 15000 lb. axles. The pig was a bolt-in fit. I salvaged the shift knob, cable, and valve from the doner, ran 3/8" copper tubing along the frame rail, rubber hose to the shift diaphragm. Once you get used to vacuum or electric, they both work fine. Just like anything else, there is a learning curve and you find the sweet spot for how much rpm, torque, clutch or no clutch, etc.
