My Cummins 5.9 powered 2007 Dodge 3500 carries a 4000 lb truck camper, has 140k and has been to Alaska twice with no problems. It has had regular maintenance, including transmission fluid and filter changes. Last fall the check engine light came on while I was hauling the camper back from Wisconsin. The diagnostic message said “low fluid pressure” but the trans and cooling fluids were fine. Light went out and stayed out, then came on again the next time I took a long trip and was climbing a steep grade. Took the truck to a trusted mechanic and he could not replicate the problem while he was driving with a diagnostic tool connected. He won’t just start replacing parts without being sure they will fix the problem. Honest guy!
I’ve just returned from another long road trip with the camper and had the light come on again. Truck still runs and shifts fine at speed, but I noticed now that when I climb a grade from a standing stop the engine revs a bit more than usual. This is a four speed 48RE transmission. If this sounds familiar to you, I’d appreciate your suggestions.
No clue personally but I thought a transmission would hold a code. Maybe you need a transmission mechanic not a generalist. The codes read may be different.
I didn’t read the link in the post above, but I’d guess it is helpful. I think you have a heat issue.
The tranny fluid is hot and some brands might handle heat better than others. If the fluid reaches a boiling point that would certainly cause low pressure. Change the fluid again and I’d use the fluid sold by the Chrysler, Dodge Truck service dept.
I’d also look closely at the transmission oil cooler. Is there anything blocking the airflow to the cooler? Is the cooler clogged and not cooling effectively? Is the cooler too small for the load you are putting on the tranny? I’d consider changing the tranny oil cooler replacing it with a larger higher capacity cooler.
“I’d consider changing the tranny oil cooler replacing it with a larger higher capacity cooler.”
Considering the relatively low cost of installing a higher capacity transmission oil cooler…I would do that as soon as the old transmission fluid is changed.