Here's the deal. I have a Corp 12-bolt that has 4.10 gears in it now. The pinion bearing is acting like it wants to head south. The engine has plenty of torue and HP, but at 70, it wants to jump in and out of 4th when climbing hills, not sure if this is because of the pinion bearing. Since I have to change the ring and pinion, thinking I may as well go with the 4.56. This will raise the rpm up from 2046 @ 70 to 2250 @70. This is gets into the power band of the motor a little better. My only problem with 4.56 is the heat generated by the lower gears. On a 40 mile trip, the 12-bolt gets hot. Any one else running 4.56 gears in a 12-bolt and do you have any heat problems with it? Running 350/700R4/NP205, turning 33" tires. Thanks ahead of time.