31x10.50x15's are the biggest I would go with out a lift and they wont rub. with a 3 inch lift you can runa 33", AND no your Tranny IS NOT GOING TO BLOW!!! I have an Auto and a Standard, never had a Problem them at all. Are you running the stock steel wheels or the "SnowFlake" OEM Aluminums?? With my Experiance with the stock wheels, Running a 31" tall tire its no good for the wear and it feels like the handeling off and on road is "tipsey", not saying It will roll over, but thats the feeling I get. I just Bought some after market 15x8 Eagle 058's that will help with the feeling I get Offroad plus make the tires wear better. AND of course Make it Look better.