My jeep is making a grinding cyclic grinding noise sometimes when going up my very steep driveway and every once and a while it makes the noise after accelerating from a stop at slow speeds (10-15 mph). The noise stops at higher speeds. Husband has changed the u joints and drained, cleaned and refilled the rear diff. Also he recently changed my back drum pads and front brakes. He mentioned how rusted everything was on the back brakes but said he cleaned them before replacing the pads. Could it be the brakes sticking and rubbing? This problem doesnt happen when turning- but going staight. Every time he has had to jack up the jeep to fix something, the noise goes away for a while and I think that its fixed. But within a week or two it comes back. Right after he fixed the back brakes, the car had a lot more pick up than "normal" and grinding was gone-making me assume it was the back brakes sticking and rubbing. But now its grinding and dragging a bit again. Ideas??