Back in the day, Jeep guys would run one size smaller tire on the front than the rear. Better variable grab and traction is heavy mud or snow. Not a huge deal since Cherokee's and Wranglers can disengage four wheel drive. Not so good for all wheel drive under any format. All tires must be the same size as a smaller tire runs at a faster rate of travel than their larger brother. Turning one wheel faster than another can bind gearing. It wouldn't take long to destroy or do permanent damage to the case.

 

they all have to be same size on 4wd or awd. it's ok on the fwd or rwd, but not on awd