OK, here goes my first post!

Have 1990 Montero LWB, 3L V6.
I found two posts covering similar issues but on different makes so I want to check with the powers before I go tearing into the TC.
When I am driving, and ONLY when I accelerate AND go over any bump I hear a vibration and hear a grinding noise at the low point in the shock depression. This noise is only when I am accelerating and only when I go over any bumps and is at the lowest point in the spring load.
On other brands they say it the 4WD TC trying to engage at the lowest point in the dip of the shocks. I am beginning to think this is the case with my unit but I Do not know where to start.
Does anybody have any experience with this?
The Drive lines are all tight, the shocks are new, the Monti only has 115K and has been in 4WD only a hand full of times in its life (My Grandma bought it new).