growling noise-1991 7.3

[nohairracing]

New to the forum, just spent a couple hours reading posts.
1991 ATS turbo 7.3 manual shift.
Truck is great in 2wd
When I lock the hubs (in 2wd) I get a growling noise around 55 mph +

If I lock the hubs and put in 4wd, I get another similar but different (louder) growling only in OD at around 65 mph. Above or below 65, no noise.

I don't know if both problems are related. I pulled off both hubs and the grease in the bearing looked good.

Any ideas? Thanks
Howard

[mr.garrett72]

i have a 96 1 ton 2wd manual tranny get same noise at 50 to 55mph have you figured it out yet

[SNOWKING89]

are your tires mached front to rear on the 4x4 if not it the diff tire sizes cause the tcase to spin at differ speed and can burn up a tcase