Originally Posted by Remerson228
The u joints may not be loose but could still be bad. I'd take the shaft out and check for looseness or excessive tightness that would indicate that the grease in the caps has dried out. you should be able to check the axles by moving them around by hand. When you get the front end in the air, grab the wheels and check for bearing looseness vertically and horizontally. Take off the front wheels and check the axle nuts for looseness.
I had the same grinding-popping sound only in 4. went away when i let of accelerator. I changed the u joints and yoke in the front shaft. the yoke was dried out and the needle bearrings were ground into dust. not a single noise after new yoke and u joints. easy fix.