I adjusted mine via my XCal2 but I think the Dealership would do it for you for a small fee . I think 97 and older had the VS gear but 98 and up can be adjusted via the PCM.

 

jump n..Thanks I like them alot, they have only seen the mud very few times but when they did I was very pleased with them..Most of the times the truck has seen any trails or mud was to go pull some buddies out....With my 285's my speedometer is pretty close to stock i think its like 1 or 2 mph off

 

It all depends on what tire you were running before. I went from 265-70 to teh 285-70 and my speedometer was reading about 3 percent high. There are several ways to adjust it. On pre 99 models, you have to change the Speedometer driven gear at teh transmission/ transfer Case. On 99 and later moderls, you can change it in teh computer, eitehr with a programmer, edge, EXCal etc, or teh dealer can do it for you.