OldGuy96

When I first start my truck (21 GMC Canyon AT4), the voltage indication is around 12 volts, but climbs to around 14.9 to 15.1 within a minute and doesn't decline to "normal" (around 13.4v). I thought the voltage regulator was controlled by the ECU. Is it a separate component that I need to replace, or is there another cause for this high voltage?

It really doesn't matter which steering box you buy as long as you're replacing the pitman arm at the same time. I had to replace the steering box on my Silverado about a year ago, and the bigger issue, generally, is which specific steering gear box the supplier has in stock at the time you go to buy it. Pitman arms are relatively cheap, and they usually stock both types, so ti's just a matter of them matching the arm and the box spline count.

I had a '96 Chevy 1500 Z71 with a 350 and automatic that had an aluminum drive shaft.

I had a similar problem with a 4WD switch and it turned out to be caused by cold solder joints on the back of the circuit board behind the selector. I few minutes with a soldering gun, and the problem went away. That seems to be a common problem with te GM electronics.

I'm interested. Location and price?

Are you sure it's the transfer case? If it will engage 4WD Hi and Lo, then the transfer case isn't your problem. If the truck won't go into reverse, you probably have a transmission problem.