I have 02 Ram2500 quadcab LB autotrans. I'm new to Dodge I bought this truck 2 yrs ago and have had some of same problems as everyone else.

5 mos ago I had install a reman vp44 and lift pump that fixed one problem. My mileage went back up to 14-16 but now is back down to 10-11. When I'm in OD the trans kicks down for a second and then up into OD. This doesn't happen all the time but when it does it's between 45-57mph.

The truck appears all stock. I need help with possible solutions. I use the truck for work so its full of tools plus the 16ft enclosed trailer I tow.

02 Ram 2500 quadcab SLT 5.9 Cummins 97k miles 4x4

 

I beleive fuel milage tends to drop in the weather you have.
Some issues that cause OD hunting:
Bad electrical connections and grounds. Clean tighten all connections
Tranny sucking air in VB. Overfill tranny by one pint. Will not hurt anything.
Electrical RFI noise. Try shielding alt wires with alum foil. Just wrap and compress around cables. Do not short positive wiring.
Internal alt issues. A standard ignition condenser connected to alt output terminal and grounded to case. Helps hide brush arcing and weak internal condenser or whatever.
possiblly the brake switch making and breaking connection from foot on pedal or adjustment.
Possiblly the output RPM sensor on OD unit.
Possiblly a faulty terminal in a connector or wiring issue.
Good luck.