msturtz wrote:
Those ratings have to do with how much tongue weight placed on the rear of the coach.
Gas coaches are notorious for having poor tow ratings. The reason for this is most RV manufacturers use frame rail extensions that are either bolted or butt welded onto the end of the chassis manufacturer's frame. This is a very weak way of attaching the extensions.
The other issue is gas rigs are usually at or near their GVWR given they are essentially limited in torque. The Chevrolet 454 (7.4L) which became the Vortec 8.1L is a great engine. However, it simply doesn't have the torque of a diesel.
Back to your situation weigh distributing hitches force some of the tongue weight forward onto the front wheels reducing the unloading of the front suspension. A very light front suspension and nearly overloaded rear suspension is extremely common in gas coaches. If you have a weight distributing hitch which you can tell because it has spring bars and a large head then it levels out the weight between the trailer and the motorhome.
Gas motorhomes typically have a very long rear overhang exacerbating the problem.
Since you are intending on towing a car behind your motorhome on a dolly you will be fine because it essentially has no tongue weight. In this case you can use the "Weight Distributing" rating of the hitch. Keep in mind that you could not tow the same car on an auto transport that did not have a weight distributing hitch. So in short you should be fine towing your car in the manner you describe. You however MUST have a separate braking system either on the tow dolly with electric brakes or if you flat tow on the vehicle itself. In most states this is a legal requirement.
Your motorhome's brakes don't have the ability to stop 4K extra weight in the back. If the tow dolly has electric brakes you will need a brake controller in your MH if it has surge brakes you won't need the brake controller.
I toured the Fleetwood factory back in 1996, and the frame extensions are the reason for Fleetwood rating the RV chassis for only towing 3,500 pounds. My car is slightly higher than the 4,500 pound limit, and my frame extension behind the rear axle is only about 18" long, so I do not have the same problems that many longer coaches would have.
How long is your coach? If over 30' that is a lot of weight to place on the frame extension. If you have a 'tag' axle, common on the 34' and longer RV's of that era, then the frame extension starts about 8' behind the factory axle (dual rear wheel one) and goes all the way to the rear bumper. The tag axle is mounted about 40" behind the center of the factory dual wheel axle, to the GM section of the chassis.
So I have a 30'11" long coach on a 190" chassis, that is about 29' long from the Ford factory. The same 190" chassis is used with a tag axle on the 36' long Southwind and Pace Arrow and Bounder. It would also come from the factory with a 29' long chassis, and have a 7' extension welded on, with the tag axle too.
It is the end of that 7' extension that the hitch is bolted on, where you would have a problem. Turning a corner, the rear of the motorhome and hitch are swung the other way as the rest of the coach is moving, and it puts a lot of stress on the frame extension. While 3,500 pounds seems to be OK, 5,000 pounds is not.
I used to tow my minivan on a tow dolly, and I can tell you they are a pain to deal with at the campground. Now I have a Ford Edge. I used to have a Honda CRV, and both of those I towed 4 wheels down. Much faster to hook up, no needing to find a place to store the dolly when in the campsite, and easier all around.
I did install a braking system on both cars. It cost me about $35. It was a cruise control motor from a junkyard car, and it's cable pulls the brake pedal to the floor. It takes a few more parts to make the power brakes work right, and connect everything, but it can be done. I get vacuum for the power brakes and CC motor from my RV engine.
I would recommend that you find a lighter weight car to tow behind the RV. You can not use a weight distribution hitch with the tow dolly to increase the hitch capacity. I would not recommend using a WD bar system with your RV anyway, the frame extension is probably to long (depending on how long your RV is).
Good luck!
Fred.
