Q. My 1999 Dodge Ram 2500 diesel with an automatic transmission has the same problems with overdrive as others I’ve read about in Trailer Life. At one point, I could shut it off to reset the computer and it would stop for a while — but not now. I also found that if the batteries were bad, the transmission would surge in and out of overdrive.
The first time was at 45,000 miles; now the truck is at 65,000 miles, and I can’t seem to stop the surging. My truck will shift through all gears fine. Once in overdrive it will start to unlock. If I stay
just below 55 mph or 1,600 rpm, it will not do it. I’ve read past articles, some of which were about a wiring harness or some switch. I need help to know what to start looking for.
— B.G., Plaquemine, Louisiana
A. There are several ways to go. My first choice would be to swap in a NV5600 manual transmission. However, you probably don’t want to hear that, so find a good Dodge Five-Star dealer, since these shops are more likely to fix the problem.
The transmission remains in overdrive and lockup as long as certain parameters are met. It can be a number of situations that cause it to unlock, such as a bad electrical ground connection, inconsistent
voltage, faulty wiring, improper aftermarket wiring, a faulty TPS — the list goes on. Finding the problem takes time and a very skilled technician, but it can be corrected.
I would recommend fixing the problem first, and then at least consider buying a manual lock-up switch for the automatic transmission, such as those sold by BD and others.
Ken Freund’s more than three decades of auto-repair experience and 20-plus years of RVing helped him author numerous books and articles on vehicle repair. In addition to RV Clinic and Performance, he writes the Powertrain column in MotorHome magazine. Ken has been a California Automotive VO-Tech and Smog-Test Program Instructor and an ASE-certified Master Automobile Technician.