I have a 2002 1500 2WD Suburban with 126,000 miles. Recently it has developed a noise in the rear end. I hesitate to say differential noise, because I am not convinced that is the souce of the noise. I checked the lubricant level and it was correct. I went ahead and changed the lubricant as recommended in the owner's manual as well as added a bottle of GM's Limited Slip Axle Lubricant Additive (PN 1052358). The noise appears to be about the same. What I am leaning toward are the tires. They are Dunlop AT21 tires. They have about 4/32" tread left with fairly uniform wear. The noise is definitely not a growl (bad bearings) and is not resonant between 40-50 (bad ring gear and pinion). Are there any tests I can do to determine if the tires are at fault, other than try another set? Thanks.