Rolling Rocks
I have a 1996 Georgie Boy on a Chevrolet P-30 chassis, and it’s like rolling along on rocks. Everything in the coach sounds like it’s going to vibrate apart. I’ve replaced the shocks and the air bags, but I have not replaced the tires, which are Goodyear G647 load range F. I’ve adjusted air bag air pressure up and down without changing the ride; however, the side-to-side sway was greatly improved with higher air pressure in the air bags. I lowered the air pressure in the tires to the minimum recommended pressure in the Goodyear tire charts, but this didn’t cause any improvement. Technicians at the local Goodyear tire shop would like to replace the tires, because they think the tires are the culprit, but this would mean about a $2,000 charge with mounting and balancing.
Chuck Lewis, F358655
Brookville, Ohio
A: The G647 tires are designed and built for use on regional package delivery trucks (UPS, FedEx, etc.). These trucks often travel as many miles in a week as you’ll put on a motorhome in a year. The tires wear like rocks, but unfortunately also can ride like them, which is perfect for high-mileage, load-carrying cargo vans, but not for motorhomes. For this reason, Goodyear recently introduced the G670 RV all-position tire, which can carry the required loads but with a comfortable ride. I’m assuming you’ve weighed your coach — you said you used the Goodyear tire inflation chart — so I suggest you replace the G647 tires with G670 RV tires of the appropriate load range. Although manufacturers recommend using the same tire all around, Goodyear’s RV Web site, www.goodyear.com/rv, recommends that the same tire be used across an axle. If your G647 tires are less than 5 to 7 years old and are in good condition, you may consider replacing the two front tires at this time. This should take care of most of your vibration worries, and you can replace the four rear tires and the spare at a later date.
Besides the tires, there could be other issues at hand, such as worn out leaf springs, reduced A-arm clearance, or fatigued front coils. If your problems continue, you may consider having a suspension specialist take a look in these areas for possible problems.
Cutting Costs?
With the high cost of operating RVs today, I am wondering if there are ways to economize in the maintenance area. I have a Cummins M11 diesel engine in my 40-foot motorhome, and I change the oil and filter about every 6,000 miles, although under certain conditions I could go up to 20,000 miles. I would think that an expensive oil filter should be good for more than 6,000 miles. I feel I may not be getting the best use out of my oil and filters with the 6,000-mile change. I also change the fluid and filters in my Allison 3060R transmission at 18-month intervals. The fluid looks clean, with no color change, and the filters cost $75. Would laboratory analysis of the oil be economical and advisable to extend the oil change interval? What are your thoughts on the subject?
James C. Lewis, F253207
Dalton Gardens, Idaho
A: You may be able to save some money by doing your own servicing. Most diesel engines can go longer than 6,000 miles between oil and filter changes, although the diesel engines in pickup trucks require oil changes every 3,000 miles. I’m assuming your Cummins owners manual calls for 6,000-mile change intervals. If this is correct, you shouldn’t vary from these guidelines. No matter how expensive the oil and filter changes are, replacing an engine because you tried to stretch the service intervals is going to cost you a lot more. Stick to the engine manufacturer’s guidelines and play it safe.
Oil analysis saves large fleet operations money, because it can predict fairly closely when oil or engine changes must occur; however, it may not be cost-effective for the individual owner.
If you have additional questions about your specific circumstance, call Cummins Customer Service at (800) DIESELS (343-7357) between 7:00 a.m. and 7:00 p.m. Eastern time, Monday through Friday, to double-check your engine’s mileage requirements.