How bad is different tread depth on rear tires?

[WallyWest]

Bought a used 2002 4Runner a few months back. Took it in for inspection and my mechanic noticed that the rear tires are different. They're both worn down enough that I'm just going to replace them, but the right one has less tread than the left. He said that's hard on the differential, even in 2WD mode. This is my only vehicle right now so I asked him if it's ok to drive for the next few days until I get tires. He said well, don't drive it more than you have to.



So should I be worried? I've gone about 1000 miles since I bought it, and who knows how long the tires were mismatched before I bought it. Last snow we had I did use the 4WD and it seemed fine, FWIW.

Is this a big deal? I know it can be for some AWD cars, but I thought in 2WD mode that it wouldn't matter.

 

[Davy180]

Are the tires a difference size or is the tread just worn out more on one side then the other? If they are within 2/32 of tread it shouldn't be a problem. If it's over that then over time it can cause a problem, your differential will think your constantly turning. As a possible temporary solution raise the tire pressure in the tire with less tread and lower it in the one with a lot of tread. To try to make them have the same circumference. As a precaution you should probably change your differential fluid once you correct you tire size.

On AWD vehicles all tires have to be the same size. On two wheel drive vehicles the tires on the same axle have to be the same size.