I have an '03 SLT 4X4 5.7L HEMI. It has OD Disable instead of the tow/haul feature that Dodge added in later MY's. Is there a service kit or software upgrade I canpurchase to change my truck over to tow/haul?

 

The newer transmissions with the tow/haul it just changes the shift points. When the truck is empty it wants to get in that next gear as soon as it can to keep the rpms down and the gas mileage up. The tow/haul keeps it in the gear longer so when it does shift it doesn't have to turn around and downshift back because it can't pull the load.

 

Yep, on my 08 it delays 2-3,3-4 shifts locks out 5th and will downshift a gear if gaining speed without giving it gas to ease the load on the brakes. Also disables the MDS.

 

^
what he said!!