1991 Suburban help

[78burb]

Specs 1991 Suburban 1/2 ton 5.7 auto 241.

Good- Upshifts fine going all speeds can feel torque converter lock up.
Bad- When letting off the gas and slow to about 50-55 there is a banging sound coming from what I think is the t-case but can't tell for sure.
Anybody have an idea? Any help greatly appreciated. Thanks

 

[Pookster]

Could be anything. Check the U-joints, take off the drive shaft, and check from there- Even if they appear ok, they could be damaged. Check the output shafts too, someties they develope wear.