I have been given my mom's 1991 Ram 150 LE. It was well cared for and only has 150,000 miles on it. However , it's having a few problems that I can't figure out. First the speedometer needle would go crazy and the odometer would roll right after starting the truck. I would smack the dash to make it stop, or have to drive over 59mph to get it to behave. Now the speedometer doesn't work at all. How do I fix this?
Also the truck won't downshift and the OD button stopped working. I did the flash code test and it comes up code 37. How do I fix this?
Thank you for any advice.