I have a 99 Suburban, 4WD with rear differential noise. I know it has a 3.73 ratio (from research done a long time ago) with a 10 bolt rear differential. 1st off.. HOW THE HECK DO YOU CHECK FLUID LEVELS? I've probed around with my fingers and can't find a filler hole or fluid check hole. I've got noise coming from the rear differential. The paint/coating looks like it's been baked pretty hard, and is peeling off. I've never done a differential before, and am at a loss to know where to start in looking at this. The noise is pretty bad. It almost sounds like when I had a brake collapse with parts scraping inside the drum. I have the sub up on rear jacks with front wheels chocked.. Ran it in drive, and the noise is loudest in the rear differntial case, but sounds loud out on the axles as well. Are there common failure points? How to check the fluid level? Is it better to just try to find another rear differential than to mess with this? I have no idea if my daughter may have caused any damage.. She took the truck off roading and ran it through soem pretty rough areas, causing a big wood stump to push the driver's side floor up about 5 inches, front bumper knocked in and up.. etc. I have no idea if she had gotten stuck somewhere and gunned it trying to get out.. or anything. She to this day denies everything, but was the sole driver at that time, and the floor just 'mysteriously' grew that hump.