OK Drive Train experts, I need you! I have a 2003 Yukon XL with Autotrac 4x4. 160K mi. I ride on Michelen Latitude 265/70 x 16's. I took a nail in the sidewall of the right rear tire which of course could not be repaired. The new tire would come in fairly cheap after getting credit for the mileage remaining on the old tire. The tech at the dealer said the circumference of the new tire would be about 1" greater than the other 3 tires due to tread wear difference, and this could have a wear/tear issue on the differential. Because I have a differential at the front and the rear there was really no good place to put the new tire. His recommendation (of course!) was to buy 3 more brand new tires at full price. I would not get any price break for the 3 new ones because there is nothing wrong with the old ones. I calculated that there would be only 0.0105 difference in circumference between the new tire and the old ones. Was the tire tech right about causing differential damage, or did he just want to sell me another 3 new tires? I figure there is easily 30K mi of life in the old tires.