I'm as happy as a clam, or a pig in poop, or whatever else is happy. With the help of member DougH6100 I transplanted a 2 speed differential from a doner truck he bought. My truck is a '57 5700 LCF, his doner is a '56 6100, mine originally was a single speed rear end, now with the 2 speed my truck can run at a more relaxed rpm at 60 mph/3700 rpm. Prior to the transplant I was topped out at 50 mph/4000 rpm. No welding/drilling/grinding or other major fabrication required, I used his original vacuum shift valve and cable/knob, I ran 3/8" copper tubing from the transmission mounted valve back to the rear axle, tee'd into my vacuum at a factory tee, added a vacuum reservoir. The system works very well, it gave me incentive to finish cleaning and painting the rear hubs, along with chrome lug nut covers from I-80 truck stop. I'll have to post some pics.
