I recently aquired a 2000 D2500 with the 24 valve engine and auto transmission. This transmission has me wondering if there is something wrong with it. Driving at 60 MPH in OD, the RPM is 1550. If I lift my foot of the accelerator pedal, the RPM immediately drops to 900, with no engine braking. If I lock-out the OD, at 60 MPH the RPM is 2350, and will drop to 1850 when I let off the pedal. The converter lock-up comes on at 45 MPH, so I assume it is working normal. Past experence while driving an auto trans has been that there should be engine braking to assist in slowing the vehicle. This vehicle has none. I plan on using this truck to pull a 5th wheel camper, but with this transmission, the truck is useless. Please help.

 

My 01 is the same way. it does not engine brake until you drop down in the gears. I also pull a 5th wheel and do not have any troubles, but I do have a nice brake controler installed.

 

Maybe you want to look at the Autoloc from BD or something similar to keep the torque converter locked up. As soon as you take you foot off of the throttle, I believe your TQ is unlocking.

 

As above, it's normal. Research "lock up switch" for a cheap fix.