RV Tech Savvy: Is Gas Fading to Diesel?


Why are most manufacturers of small motorhomes going to diesel, especially on the Mercedes-Benz Sprinter chassis? We would like to trade our 2016 van for a 24-foot Class C. The only choices are big Ford/Chevy gas chassis or diesel chassis. Our Pleasure-Way Lexor is on a RAM ProMaster chassis, which runs on gas and gets about 17 mpg. This is what the Sprinter gets, and diesel costs more at the pump. Mercedes may be a good long-lasting engine, but at our age we can’t justify the several thousands of extra dollars to purchase and maintain it. Any ideas why more small RV manufacturers are not using the ProMaster on vans and smaller 24-foot motorhomes?

Mary Burnett | Kissimmee, Florida

Not all manufacturers are going that way. Our January issue addressed this topic very well, with the article “Chassis Connection,” starting on page 34. You may be completely overlooking the Ford Transit chassis, which offers two different gasoline engines and one diesel. The Mercedes-Benz Sprinter chassis is widely sold in Europe, where the cost of fuel is much higher than in the U.S., so fuel economy is an important design factor. Diesels typically get in the neighborhood of 30 percent better fuel mileage than a closely equivalent gas engine, and in Europe, diesel fuel is typically cheaper than gasoline. This is why the Sprinter came with a diesel. The RAM ProMaster chassis is designed mainly for the North American market and offers a 280-hp gas engine aimed more toward that audience. However, for 2019 Mercedes is offering a 2.0-liter four-cylinder turbo gasoline engine with 9-speed transmission.


Swaying Class C

We have a 31-foot 2011 Jayco Greyhawk motorhome on a Ford E-450 chassis. I have added aftermarket front and rear suspension upgrades. These consist of front and rear stabilizers. I installed these to reduce sway and rocking, such as while being passed by an 18-wheeler, or when encountering wind gusts, but the motorhome still has more sway and rock than I would like. Wind is still really bad. I know I cannot get away from wind or passing big rigs. Without spending a ton of money, what would you suggest next?

Gary Hanna | Spokane Valley, Washington

Your motorhome has a long rear overhang and a lot of side surface area, which is a recipe for swaying. The heavy rear acts as a sort of pendulum. You are basically fighting against physics and need to understand that you may never completely eliminate swaying. I assume the stabilizers you installed are sway bars or, more correctly, “anti-roll bars.” There are several manufacturers of these, including Hellwig and Roadmaster. You might consider a SuperSteer Rear Trac Bar, which is designed to eliminate unwanted and uncontrolled side shift of the rear axle. I would have gone with this first. The URL is https://supersteerparts.com/product/trucks-vans-suv/ford/e-350/e450-chassis-rear-trac-bar. Roadmaster also makes the Reflex Steering Stabilizer, which uses springs to return to center (www.roadmaster inc.com/products/rss/reflex.html).

The ultimate fix is a product called LiquidSpring, which is a Compressible Liquid Adaptive Suspension System (CLASS). Used in the emergency vehicle and RV markets, the LiquidSpring suspension is quite effective at dampening sway, at a premium price. You can see our review of the LiquidSpring suspension at www.motorhome.com/motorhomes/motorhome-gear/suspension-transformation/


Rough Ridin’ Rambler


We have a 2007 Holiday Rambler motorhome with a very hard ride, especially in the front. I replaced shocks and had the air bags adjusted, with no improvement. Should I consider sway bar bushings or something else? What else could be causing the sound and feel of bottoming out over bumps?

Richard Corbin | Springdale, Arkansas

In 2007, Holiday Rambler made a wide variety of models on several chassis, including Ford, Workhorse and GM, plus the diesel pushers on heavy-duty chassis. Without knowing which one you have, it is difficult to give specific information. Worn-out sway bar bushings might result in a clunking sound when negotiating turns when the motorhome tries to lean. However, they won’t significantly affect ride while driving straight.

Tire pressure can greatly affect ride quality. To determine the correct pressure, weigh the motorhome when fully loaded for a trip, including fuel, water, LP-gas, cargo and passengers. Obtain the tire manufacturer’s load-inflation table for the tires. This can be found at tire dealers and on the manufacturer’s website. Adjust all tires to the pressure listed for the actual weight on the individual tires at each position. If you can’t weigh by wheel position, a less accurate method is to take the axle weight from the scale report and divide that number by the number of wheels on that axle. Then adjust the pressure for that and add 10 percent. I suggest checking for sagging or broken springs, which could cause the suspension to bottom out. While you’re at it, check the rubber jounce bumpers. If they look like they are rubbed clean and appear to be getting used regularly, put some paint on one, and after a test ride, which should include bumps and dips that wouldn’t bottom a suspension in good working order, recheck them for paint transfer. I suggest you have an experienced RV or suspension technician test drive it and give you a professional opinion on ride quality and needed changes.


Overfilled Transmission


We have a 2014 Tiffin Open Road Allegro 31 SA with 17,000 miles on the odometer. Recently I had the transmission filter and fluid changed because we tow a dinghy and wanted to ensure that the transmission is meticulously maintained. We drove approximately 200 miles when, upon entering a freeway, a huge cloud of smoke billowed out from under the coach. I continued to drive slowly an additional 50 miles (with no further smoking) in order to get to a Ford dealership, where they diagnosed the problem — the transmission had been overfilled by 1½ quarts and the fluid had been thrown out the overflow. My owner’s manual states that overfilling a transmission can damage it. How can I tell if damage has occurred? Can damage occur in 250 miles? Did the blowing of fluid out the overflow valve damage anything? Once at home (additional 300 miles) the check engine light came on. It was for an oxygen sensor on the left bank. Could this be related?

Ken Schiltz | Prescott, Arizona

I’m not sure how the dealership could diagnose how far the transmission was overfilled when much of it had been ejected, but in any case, it’s unlikely that any damage occurred based on your explanation. Sometimes a high fluid level can cause seal leaks, but usually you would notice operating problems right away.

It’s unlikely that any transmission fluid affected the sensor that is far forward of the overflow outlet. Besides that, aside from physical damage to the exterior, oxygen sensors typically only fail due to foreign substances in the exhaust stream. In other words, if your engine had ingested the transmission oil, burned it and sent it down the tailpipe, it would be possible that the oxygen sensor was damaged, but this was not the case. You did not mention if the oxygen sensor was replaced or not, but if it wasn’t, I suggest recording the “Check Engine” error code and then deleting it. If it doesn’t reappear in several hundred miles, it was probably just a quirk. Finally, keep in mind that most transmission failures are caused by excessive heat. Consider using a quality synthetic fluid (which is more resistant to heat breakdown) if you are towing, particularly if it is a heavy vehicle or trailer.


Towing the 2019 Malibu


Have a tech question?My Chevy dealer says I can flat tow the 2019 Malibu with a turbocharged 2.0-liter engine and nine-speed automatic transmission. The 2018 wasn’t listed as being towable. I’ll consider ordering a 2019 Malibu Premier with that engine/transmission combination if you confirm the dealer’s info.

James Brossard | Bellevue, Washington

You’re in luck. I contacted Chevrolet directly on your behalf (800-222-1020) and it verified that this model with the 2.0-liter turbocharged engine is the only 2019 Chevrolet Malibu factory-approved for towing. Whenever considering a new vehicle for dinghy towing, it is always a good idea to consult the owner’s manual, as we did. The applicable information about dinghy towing is on page 316. Among the restrictions, it calls for the negative battery cable to be disconnected. Therefore, you’ll need a charge line from the motorhome to power most auxiliary braking systems. You’ll also need to run the vehicle at the beginning of each day and at each fuel stop for about five minutes, and must not exceed 65 mph while towing.


 



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