If your tires are not the same size, you are going to experience a number of issues when shifting into and out of 4x4.

Basically, tires on each axle must be same size to reduce wear on ring and pinion and spider gears in differential.

And, tires on front and rear axles need to be the same size to keep binding and gear wear to a minimum.

Tire pressure differential on same size tire can also cause shifting/binding issues.

So, start by installing the same size tires with correct air pressure and see if that corrects your problem.

John Stewart
Editor - 4x4Wire.com
Editor - 4x4Voice
Editor - MUIRNet-News
President - BlueRibbon Coalition