"Someone"...A mechanic told me to lock in the front hubs once every 6 months and drive around at 45 mph to get everything "Hot"...1988 4X4 truck 148 K.....If that is good advice, do it on dirt or is pavement good ?...Thanks Charlie

 

It's to keep everything properly lubricated. It can be done at any speed, dirt or pavement doesn't matter as long as your not in 4wd.
I've always used 4wd so often this isn't needed for me.

 

yeah, he told you correctly.....

 

I try to do it a little more often than every 6 months. The theory is that, without motion, eventually gravity causes the oil film on the parts to drain off, exposing bare metal to the atmosphere and to rust, etc. Churning things up every so often recoats all of the parts with oil. In the aircraft industry, they told us engines should be run at least once/month to keep things lubricated and protected. Running it long enough to get hot helps drive the water out, as well.

 

Can also just put it in 4HI with the hubs unlocked to accomplish the same thing.

 

Most likely. However, with an open differential, there's no absolute guarantee that both CV axles will spin. If one is a lot stiffer than the other, the stiff one will stay stationary and the differential will drive the other one at 2x the speed. I think that's generally unlikely, but conceivably could happen.

Test this out by crawling under the truck with it in 2wd and hubs unlocked, and try rotating the drive shaft by hand. If both CV axles turn at the same rate, then the resistance is balanced enough that your suggestion will work. If they don't, you should probably figure out where the extra drag on the slow/stopped one is coming from.

 

True ^^. But if one CV doesn't spin the other CV WILL NOT spin twice as fast. It will turn at normal speed.

 

Nope. If you have an open diff, the sum of the speeds of the CV shafts = 2 times the ring gear speed. If one slows down the other one speeds up. That's what makes it go around turns smoothly. If one CV stops, the other goes at double speed.

 

RJR's got it.

Need to play with an open diff to see for yourself.

 

User's manual recommends driving in full 4WD regularly. I believe it's 10 miles a month. Of course, paved road is NOT recommended when in full 4WD.