Is it possible to change out your rear axle to get a higher weight rating - maybe put a 250 rear axle in place of the 150 rear axle? Our rear axle is rated for 3575 and we would like to increase it to about 4200#.

 

Technically, you can do the swap, but you still have to maintain the factory GAWR/GVWR that's on the door jamb sticker. It would be able to handle more weight of course, but you still have it attached to a 1/2 ton frame.

 

Ya, its not just about the rear axle at all. You have to consider braking power, frame, suspension...