94 4wd light flickers at high speed

My 94 has just started where the 4wd light will flicker at higher speeds and under acceleration. At semi/lower speed I can hear a whine like it's trying to engage. Not sure what's going on. Anyone have a clue? Btw, i have the manual 4wd shifter in the floor. Thanks for any advice.

 

I would start with a fluid change at the front/rear diffs and transfer case. It’s trying to tell you something...You can get the crush washers from EBay for like ten bucks. Torque specs are rear/36, transfer/25, front/20 or close to that.