No not necessary... Old voodoo from the days of vehicles with locking hubs.

 

Yes, I had an 87 Chevy 4x4 with the NP 208 t/case and WARN manual locking hubs. What a PITA to get out and lock them in especially when you got stuck! One of them was so worn out it would occasionally lock itself in when going down the road, causing it to pull to one side and feel wonky on turns. That was before I bought a jeep. I believe the reverse bit was if you had automatic hubs.

The worst part was they didn't save you any gas mileage either. That tank I had only got about 8 mpg! Nice 350 though.

 

A 4x4 with locking hubs wouldn't handle any different in 2wd with the hubs locked than our Jeeps do in 2wd, since the Jeeps have full time hubs the front driveline is always spinning. I regularly drive my F250 with the hubs locked and it makes no difference in fuel mileage or steering.

 

Really depends on the transfer case.

 

Yeah, but only one side was locking in by itself. It had the same feeling as a dragging brake. The mileage was the same both in and out of 4wd. You might as well have poured fuel down the carb throat! If the engine stalled there was no way I had enough strength to turn the wheel because it had so much resistance. AND it had a tilt wheel that was flopping around because the guy that owned it before me used it to pull himself up into the cab. Did I tell you it had 33 X 12.5's on it?