Tom

Hello   Tom,

Q My father suggested I write you because he listens to your national radio

show on XM radio. I own a 1982 Ford F-150 pickup truck with four-wheel
drive. I put 311050R17 tires on the rear and 21570R15 tires on the front. This
made it look jacked up. It drove fine until I put it in four-wheel drive. The
truck acted like the brakes were on, and it came to a stop. Now when I put it
in four-wheel drive I just hear grinding and it doesn’t move. What happened?

Josh—Pineville, North   Carolina

Josh,

A You destroyed the transfer case. This vehicle is equipped with part-time

4WD. This means that when the vehicle is shifted into four-wheel drive, all
four wheels are locked together and turning at the same rate of speed. The
transfer case has no way of differentiating between the two tire sizes and the
different rpm they turn at. When you put the truck in four-wheel drive with
the tires turning at different speeds, the transfer case gears bound up against
each other and eventually failed internally. It’s no wonder the truck acted like
the brakes were on. The transfer case was twisted and binding up internally.
Sorry to be the bringer of bad news, but you probably have to replace the
transfer case. Next time, make sure all four tires installed on the truck are the
same size.