Ive got a 91 toyota 4x4 with locking hubs, I got all new inner and outer bearings and new upper and lower ball joints from my mechanic because it was making a grinding noise on the front driver side. I thought it was the cv axels but my mechanic said there still good . It still makes the noise here and there but only when the hubs are locked in?? Any help would do p.s I live in Alaska and it seems to do it more in the cold(15 below)

See if this helps:

. Change front differential fluid, using Mobil 1 SAE 75W-90 Synthetic Gear Lubricant.

. Change transfer case fluid, using Mobil 1 Synthetic Multi-Vehicle ATF. If you have a manual transmission, use Mobil 1 SAE 75W-90 Synthetic Gear Lubricant.