Transmission Position While Towing
May 20, 2015
Filed under RV Tech Q&A
I have just read that a 2010 Jeep Wrangler must be placed in park while being flat towed. I own a 2006 four-wheel-drive Jeep Liberty, and in the past, I have flat-towed it with the four-wheel transfer case in neutral and also the transmission in neutral. By doing this am I harming the transmission? Should I be putting the transmission in park instead? Thanks for any help.
Russell Armstrong | Henderson, Nevada
Russell, always refer to the owner’s manual for towing recommendations. The transmission should be in park if it is an automatic and in gear if it is a manual gearbox. When a transfer case like yours is being towed, a small lubrication pump inside is spun by the driveshaft. However, due to the viscosity of the oil in it, even in neutral the back of the transmission may be driven (turned) somewhat. (Often it is not enough to cause damage, but you’re taking a chance.) The reason this is not good is that many automatic transmissions generally don’t receive sufficient lubrication if they are towed, as opposed to being driven. A manual gearbox in neutral doesn’t spin the cluster gear, which circulates oil on its teeth up onto the other gears and parts. Most automatic transmissions rely on the front pump, which is engine-driven, to circulate cooling and lubricating fluid. The automatic won’t spin internally if it is placed in park. I recommend using high gear instead of first on manual gearboxes, because if the transfer case ever gets bumped out of neutral, it won’t over-rev the engine while being towed. I have seen this happen a number of times, which is why I suggest using high gear instead of first to keep the transmission from spinning.
While driving, the left inside dual tire came apart on my 27-foot Lazy Daze motorhome just south of Susanville, California. The tire was original equipment on the motorhome, which was about 5 years old. The motorhome is parked for about six months of the year, and I park the tires on 2-by-6 wood planks nailed to ¾-inch plywood so they don’t sit on the wet ground (in case of rain). I keep the tires covered and inflated to 80 psi, as indicated on the door placard. I thought they would last longer than this. Am I doing something wrong? Would the tires last longer if I jacked the motorhome up? I would appreciate any advice you can offer, as the new Michelins cost about $292 each out the door at my tire dealer.
Kent Williams | Hesperia, California
I know that parking the tires on top of boards is recommended by many folks as a way to protect tires and to keep them from sitting in water for an extended period. However, sitting in one spot for six months every year can be really tough on tires. Parking in one spot causes flat spots on the tires and they often form cracks in the rubber at the point of contact. I recommend moving it at least a few feet every couple months. I’ve seen many vehicles that sat still for a long time during storage and repairs, restoration, etc., suffer a series of tire failures after sitting for extended periods.
Although your coach may have been only around 5 years old, the tires could have been a year or two older from sitting in a warehouse, etc., before installation. Tire manufacturers generally recommend replacement after about seven years. It would be necessary to read the DOT date codes stamped on the tire sidewalls, which are a four-digit number. The first two numbers are the week; the second pair of numbers are the last two digits of the year. (For example, 3008 would be the 30th week of 2008.)
The pictures you sent me show that the tread peeled partly off the carcass. This can happen due to heat, and this process is accelerated if a tire ever is run with pressure that is too low. This might occur if inflation was overlooked sometime, or pressure was lost due to a slow leak, etc. The tire may be weakened and the failure may occur later on. It’s also best to weigh each corner and inflate the tires according to the load-inflation tables provided by the tire manufacturer for that specific tire, based on the actual weight it is carrying fully loaded.
Diesel Won’t Start When Hot
We have a 1999 Georgie Boy Cruise Master motorhome. It has a 5.9-liter Cummins diesel engine. For the last three years I have been fighting a starting problem. The engine starts great when it’s cold, but when it gets up to operating temperature and I shut it off, wait a little and try to start it again, it won’t start until after it has cooled down. My diesel mechanic said the electronics on the main pump were breaking down when it is at running temperature. I changed the pump, but that didn’t help. I then changed the lift pump, but it still won’t start when it is at operating temperature. I took it to a Cummins shop to scan and they said it looks like a bad main pump. A solid $250 later they changed the main pump again! It still won’t start when it’s at operating temperature. The crankshaft position sensor was changed, and also the starter, but nothing has helped. I’m going broke on this Cummins, can you help please?
Walt Johnson | Bayview, Idaho
It makes sense that the electronics fail when hot and start working when they cool down, but if the engine cranks over at a normal speed at operating temperature but won’t start, the starter should not have been changed. Whoever sold you on that should refund your money. When a diesel engine is warm and has good compression and cranks over normally, but won’t start, it pretty much has to be a fuel delivery problem.
I’m surprised and disappointed that the Cummins dealer didn’t stick with the problem and fix it. They should be looking for fuel delivery at the injectors when the engine is being cranked when it is warm. There is a module which provides an OK-to-start signal, which can be affected by a blown or corroded fuse, so check all the fuses.
A starting problem can also be caused by a leak in either the inlet or the return side of the fuel system. This type of leak can allow air to enter the injection pump resulting in starting issues. A rubber hose connecting the pump to the steel hard line can be the source of this kind of leak. Also, follow the lines from the tank to the engine.
I’d like to hear from readers who have experienced this problem and solved it.
We have encountered a bit of mold in our 2007 32-foot Class A motorhome. Mold is present on the ceiling in the kitchen, and the bottom of a cabinet is black with mold under the vinyl cover. All the wood is overlaid with a white vinyl product instead of being painted, stained, etc. What should we do to stop the mold?
Thomas Jackson | Gainesville, Florida
First, you need to determine where the moisture that is causing the mold is coming from. A humid climate, especially a warm one, can allow mold to grow inside a motorhome quite easily. During storage, it is helpful to use a dehumidifier or desiccant product to keep the air inside the coach dry, and you may also consider opening the roof vents and using a roof vent cover to allow air to circulate. Beyond that, make sure there are no points of entry for moisture inside the motorhome, such as a roof or appliance leak. Mold on surfaces can often be removed with cleaning products that include bleach–but remember, mold can be hazardous to your health. If you are not comfortable removing it, there are many companies that offer mold and mildew removal services. You should be able to find one in your area.
Cab Heater Comment
I’m responding to “Motorhome Cab Heater Issue” in the February issue. I own a 1999 Damon Ultrasport DP. The coolant circulates from the rear diesel engine, in a supply line and a return line, to the cabin heat exchanger. In each line (underneath the coach) there is a shut-off valve. If these valves are closed (normal summertime travel) no heated coolant will reach the heater core. This is worth checking.
Richard Davis | Houston, Texas
Even if a valve was partly closed this could cause a lack of heat. Conversely, this is also a good thing to check in the hot weather too; make sure the valves are closed so the air conditioner doesn’t have to fight against the heater in the cab.