Engine/Transmission (1994 - 1998) Hard transmission shifting on my 95 Ram 2500 Cummins

I have a 95 Ram 2500 Cummins with an Automatic Transmission. In the mornings when its cold (under 40 degrees F) and I leave for work, the truck wont shift into its last 2 gears, therefore im stuck driving 35-40mph for about 3-5miles in a 65mph zone. After it gets those last gears it gets em fine for the rest of the day, its just that first time. I only have this issue in the winter, it works and shifts fine in the summer (I have not used a pan heater, to see if that makes a difference). I am running Amsoil synthetic ATF and every thing else about the transmission works great, it pulls my 12,000lb 5th wheel and horse trailer with ease. Any ideas on what may be going on? Could this get worse to the point of needing a new transmission? Thanks!

 

Not warm enough yet

I have a 1995 2500. These older(stock) transmissions need to warm up to 120°F before they shift like I think is normal. When it's cold it takes a long time to warm up enough to shift normal.

 

That is correct, the transmission uses one of the shift solenoids to measure the fluid temp. The controller waits until it sees 50DegF on the fluid temp (uses the solenoid coil as a restive temperature sensor) until it will let the transmission shift higher than second gear. Rest assured, it's normal and it's a good thing for your transmission to do. You can help it warm up a little faster if you idle the truck for a while before you take off (idling doesn't do a lot for warming a diesel, high idle helps some) and make sure the transmission is in Neutral. Dodge transmissions don't pump any fluid around in park so if you want to warm that fluid up a bit it has to be in neutral, that's also why these truck have to have the transmission fluid level checked in neutral.