Tow/Haul

Phil,

You have a point when you say our RV's aren't built for off-road use and such use requires different construction.

My point in this discussion is that any ordinary C can twist. Only a matter of degree.

I mentioned our Jayco's STEEL house frame. That seems to be why that very basic 31-ft, no slides, limited features inside, no basement, weighs so doggone much.
On the truck scales, 4500 Front and 9000 Rear, loaded and occupied for travel, full fuel and water, empty waste tanks. That was a big part of my decision to upgrade the front axle from 2002 to 2012.

John,

Interesting observation on your door jamming when jacking up your rig.

I notice from you signature that your rig is about a 31 footer on the E450. This is of course a heavy unit and probably loads the E450's chassis and frame severely, which stands to reason would show up under jacking situations in ways that you describe.

We level our 24 foot Class C a lot when camping using up to five leveling step-blocks to get three-point leveling. For instance, all four rear tires and one front tire up on blocks in rough or tilted drycamping spots. We've never incountered a jamming coach door during any of our leveling operations at a campsite. Perhaps your observation makes my point about the E450 chassis helping to prevent coach structure deformation when the E450 is used under smaller and lighter Class C rigs ... that otherwise could do just fine with the E350 chassis under normal camping situations where surfaces under the motorhome don't tend to twist one end of the motorhome in the opposite direction of the other end of the motorhome.

Expedition RV vehicles deal with the issue using of course both very heavy duty vehicle frames, in conjunction with coach structure mounting schemes that eliminate transfer of frame torque to the coach flooring or it's walls.

Body and Frame twist amazingly easily. I jacked ours just enough, under the outboard end of the rear axle, to slip the wheels off. Coach house door was jammed. We even have a steel superstructure attached to the Ford frame that forms the "slab" the rest of the house is built on.
Even with "biaxial" levelers, I notice that the sidewall is twisted sometimes after we level on a site.

FWIW, I've countered my E450's rear differential ratio slightly by increasing the diameter of the tires, which gave me about 0.6 inches more ground clearance for off-highway desert use. I would have went even larger on tire diameter except for the DW not wanting to climb too much higher up into the cab. We still get great slow speed and steep slope crawling with minimum tranny slippage and heating, however, so I've not completely negated the E450's lower rear differential ratio.

The fender wells and suspension could even take a lot taller tires. One Class C owner in these forums went up to 235/75R16 Load Range E tires all around, which netted him great ground clearance plus a much better weight carrying margin with these tires even though they were still rated as Load Range E. Apparently what a given Load Range rating provides goes up in lbs. with larger tires even though they still carry the same Load Range designation. This was news to me until I researched it before putting on new tires a couple of years ago.

I'll do some more research on my own to nail down E350/E450 chassis differences for Ford's latest model year. If the differences are indeed less than when we bought our Class C - then it's even better that we went with the heavier duty chassis back then.

I give a lot of importance to a seemingly minor difference - the E450's thicker frame. This helps to keep the coach floor on a constant plane when traversing rutted roads because front-to-back frame twist will be less due to it's added strength under any given coach weight it's supporing. Front-to-back torsion forces on a standard Class C coach's structure are a no-no.

Agree w/ JD that aftermarket sway bars were an improvement, even on the E450.

I'm going to say it loud and clear: I find the E450 rear gearing perfectly appropriate for small class C. I'm one that in general prefers tall final drive ratios. I do not like racing engines at cruise. A small C is still breaking a lot of wind (haha). It is not some ridiculously easy load for an E450...far from it.

My experience in driving TorqShift-equipped Fords is:
1. F350 4x4 with Bigfoot slide-in camper
2. E450 30-ft Class C
In regular Drive, I found the shifting "manners" of both transmissions to be nicer than the 4R100 in our own Class C.
In Tow/Haul, the transmission showed off its smarts, but sometimes when I would have just as soon it didn't. For example, it was nice to have it gear down on steep downgrades to try to hold speed down to what the Cruise was set at. But, I usually didn't like it gearing down on light braking.
So, in the Pickup, TH was "interesting"
In the C, I found it "helpful"
EDIT - Both were V10's, so the Pickup had the 3-valve 362-hp engine while the C had the 2-valve 305-hp version. The C still had adequate power even on the grades into and out of the Kenai in Alaska.

Several of the 350/450 differences have gone away. 350 got a wider rear stance not long ago and also hydroboost brakes. 350 didn't have rear disc brakes but now does. Also now has rear sway bar like 450 always had. To me that's no big whoop since all of Ford's OEM bars are inadequate for an RV anyhow. 350 can also have a 5000-lb capacity front axle. So, in late models, yes, 450 has the huskier frame, but about the only difference most of us would ever notice is rear axle capacity.

pnichols wrote:
What one "gains" with the E450 chassis over the E350 chassis - with an RV coach's raw weight that doesn't require it - is (at least for my model year):

1) Larger brake swept areas.

2) Thicker frame steel.

3) Increased transmission fluid volume.

4) Hydraulically assisted power brakes instead of vacuum assisted.

5) Wider rear stance.

6) Lower rear differential ratio.

All of these differences provide long term advantages and are well worth the extra dollars we had to pay for the E450 chassis under a small Class C. I advocate "buying a heavy duty vehicle and using it in a light duty way" as the best way to help ensure safety and long term reliability with lesser maintenance.

There are ways around the less mileage and rougher ride of the E450 chassis, but very few affordable ways around having a lighter duty chassis to begin with.

Not quite...

According to the Ford website for my 2011 E-350 (Compared with the E-450) chassis:

The brakes are exactly the same.

The frame sections are larger on the 450, .02" thicker. :R

The website does not address trans fluid volume but it is the same trans.

Yep a wider stance.... but not by much.

Like I said you need the lower rear end to do the work the 450 was designed to do but on 24' or less it is just overkill that reduces ride quality and mileage with no appreciable benefit. Carrying around the extra weight to support a job that that you will never need it to is simply a waste. Your reliability and maintenance will be no better with a 450 than a 350, If anything the 450 has to work harder than a 350 to just get on down the road.

My 350 has 3,368# of payload, 1,450# of which I don't even use fully loaded and it has the 55 gallon fuel tank. Advocate for the 450 on small C's all you like it is still overkill. We usually agree on most issues but ranting that your 450 is superior to the 350 is an inaccurate generalization.... and as I frequently point out:

Opinions and YMMV.

:B

What one "gains" with the E450 chassis over the E350 chassis - with an RV coach's raw weight that doesn't require it - is (at least for my model year):

1) Larger brake swept areas.

2) Thicker frame steel.

3) Increased transmission fluid volume.

4) Hydraulically assisted power brakes instead of vacuum assisted.

5) Wider rear stance.

6) Lower rear differential ratio.

All of these differences provide long term advantages and are well worth the extra dollars we had to pay for the E450 chassis under a small Class C. I advocate "buying a heavy duty vehicle and using it in a light duty way" as the best way to help ensure safety and long term reliability with lesser maintenance.

There are ways around the less mileage and rougher ride of the E450 chassis, but very few affordable ways around having a lighter duty chassis to begin with.

"This reminds me of a subtle point. A Class C coach (like tpi's and ours) that lightly loads an E450 chassis may need less use of the Tow/Haul mode's off-throttle downshifting advantages because normal engine braking is stronger. Since an E450's rear differential has a lower ratio (4:56) than the E350's, the E450 motorhome's overall engine to rear wheel gearing ratio is lower. Hence the engine will hold it back better when off the gas coming up to stops or when off the gas going down grades.

This is another reason I advocate use of the E450 chassis on smaller Class C rigs that, from a pure weight perspective, could get by on only the E350 chassis. "


The performance of the E-350 is hardly a matter of just "getting by". The reason the E-450's have the lower rear end, 4:56 vs the 4:10's of the RE-350, is all of the extra weight. Typically the 450's are found on larger to much larger motorhomes which necessitates the lower gearing to handle the load. On a Class C under 25' a 450 is overkill but if you want less mileage and a rougher ride by all means go for it, but there is little if anything to be "gained".

As always.... opinions and YMMV.

:C