Grining Noise On Accel Only

[twags6]

This is my first post here and I'm having a problem with my mom's 96 K1500 suburban. It has a grinding noise coming from either the t-case or front diff only when accelerating forward. It sounds like somebody trying to shift a manual trans with the clutch half way out, grinding the gears. We changed the fluid in the t-case (old fluid was dark red, no shavings) and checked both the front and rear diffs (needed a topping off). The only time the noise goes away is if you shift into 4wd or 4lo (no problems shifting it). I've searched this section and only found one person with a problem similar to this. Any suggestions? Its got an auto trans and the NV243 t-case with the pushbuttons on the dash.

[parker01]

I have a 95 GMC sierra with the same problem. It also does it in reverse backing up a steep hill. I have changed tranfer case fluid and transmission fluid ,made no difference. My transmission is a L460E and the New process transfer case. Before the trans downshifts I can hear it also. I suspected it was the trans ,because I have 179,000 on my truck. May need a tranny rebuild.

[Zembonez]

Wonder if the noise could be from a front halfshaft?