Hey, guys its been awhile sent I have been on the site. I sold my 03 2500 cummins due to a vibration that the dealer could not fix. That has been 4 years ago. I'm now looking at a 98.5 to 02 cummins. Is there a difference in the 4x4 unit on the 02 vs the earlier ones? I was told the fuel mileage on the earlier ones gets better mileage due to this. Trying to find out some info on that. Thanks ahead of time.