c4RunnerSR5

Hello, new guy here. Owner of a 1999 4Runner SR5 3.4 V6, automatic transmission.
I currently have a problem with my truck. When reversing in 4x4 and under heavy load there is a loud squealing type noise. Someone outside of the truck said that it came from the rear or middle.
There is no noise when I reverse in 4x4 on a plane surface.
In 2wd everything is normal as well.
Help would be greatly appreciated.

Thanks

Flash319

Id be looking at front drive shaft transfer case area. Reverse under heavy load is not a very good thing to be doing. The torque is twisting everything causing the t-case and diffs to twist with the driveshafts as well. I bet something is rubbing.

c4RunnerSR5

Thanks for replying. I will look into it.