It's your differential working 100x harder than it should be.The differential is there so that when you turn, the inner wheel is spinning at a slower speed than the outer wheel. But when one wheel is smaller (how much smaller are we talking about) then the differential has to work constantly to keep the smaller wheel turning faster to keep up with the bigger wheel. Add in RTAWD, it's a big mess waiting to happen. If your car is only FWD, I'd put the two mismatched on the rear, if it's AWD, i'd stop driving, regardless of what the excuse may be, as long as it's not life threatening.
97 Saturn SL2
99 Acura 3.2 TL
08 Honda CR-V
