Happy Hippie Love Wagon Too Shifty

I am a dentist. My wife and I recently acquired a 1990 Coachmen Class B motorhome, built on a one ton Dodge van chassis, by trading a set of teeth for it. It has a 318 cubic inch v-8 and a four speed automatic transmission (fourth gear being an overdrive gear), and has about 76,000 miles on it. It is, incidentally, purple and white and covered with plastic stick-on flowers and various sayings like “Love” and “Peace” and “One Day At A Time”. For the past two months we have been working our way through various repairs too numerous to mention. We think we are nearly done, but one problem persists. About a half-hour or an hour into a drive, at highway speed, it suddenly, and for no apparent reason, downshifts into third gear. It does this regardless of the terrain. We could be going uphill, downhill, or just cruising on the flats. If the cruise control is on, it shuts off. Then the transmission shifts back and forth between third and overdrive, spending a few seconds in each for a few minutes before settling down and behaving itself until the next episode, which might be later in the same trip or might be the next week.

This vehicle is rather heavy and a bit underpowered, so climbing hills, even at our low elevation, is a challenge for it. However, even if I push hard on the accelerator, I can’t seem to get it to downshift until the speed has dropped off dramatically.

My local mechanic doesn’t seem to know what the problem is, though he has speculated about something he called a “throttle position sensor”. In all fairness, he has had plenty of more pressing issues to deal with first, such as ball joints, the idler arm, and a fuel tank leak. I read something online about a “kickdown cable”. Can you advise me on what to do? Thank you.

P.S. We get a lot of attention with this vehicle, especially when we visit our new grandson, parking overnight in our daughter’s driveway in residential St. Paul. People seem to look disappointed when two late middle aged grandparents with short haircuts, regular clothes, no beads and no tatoos get out. I’m thinking of getting one of those theater smoke generating machine.

You might also consider some 3M decal remover. It helps to soften the glue on the decals so you can more easily remove them. A hairdryer may also be helpful.

Sorry, I have no clue about your transmission woes.

I have a suspicion as to what the problem might be. It might be working harder than you think.

You need to take it to a truck scale and get it weighed when it has all the stuff you put in it for a trip. Then look for the weight rating (in most motor homes, it’s on the wall of the closet in the bedroom). I wouldn’t be surprised if you’re grossly overloaded. Class B and C motorhomes are notorious for this, because after all the coach stuff is stuck on the chassis, you only end up with a few hundred pounds of cargo carrying capacity. Once you put food and clothes in there, you’re usually overweight.