I drive a 2004 Dodge Durango (Hemi). We live on a VERY rural washboardy road. A few months ago, I started getting the following check engine lights - P0720 OBD-II code malfunction in the output speed sensor (most common); P0731 gear incorrect ratio (a few times) and P1790 transmission fault that occurs directly after shifting (one time). I took my Durango into our regular trusted mechanic who diagnosed low transmission fluid and he added a quart. Then I had another mechanic that wasn't booked out as far as my regular mechanic change the filter and transmission fluid. He also diagnosed a squirrels nest on top of the transmission but he did not have the time to drop the transmission to remove it. So I scheduled an appointment with my regular mechanic for a few weeks later. He checked the fluid and it was about a quart low again. Then he dropped the transmission and removed the squirrel nest. He also checked the wiring harness and no damage was found. After that (this was on Sept. 16th), the check engine light did not come on again. Since I have a craft show in about a month and will be towing an enclosed utility trailer down on a Thursday and home on a Sunday, plus driving back and forth Friday and Saturday (200 mile round trip plus several steep hills on the highway), I decided to get a 2nd opinion yesterday by a mechanic that regularly works on Dodge automatic transmissions. He found no issues with the wiring harness or any other issues other than the fluid was over a quart low. I told him that it had been filled on September 16th. He found no leaks when he inspected the transmission and lines. He told me at that point, just to regularly check the fluid and make sure it is full. Does anyone have any ideas what might be causing this to happen or have had similar issues??

 

The fluid is going somewhere..... Where becomes the question. I would be checking any other fluids it could potentially be interacting with, like, engine coolant......

 

Thank you.