Chinook RV

Good point, Scott. My '99 does have the Dana 70, which has a rated capacity of 7,500# But stepping back from the axle specifically, I don't know how much changing the rear axle/rating would accomplish given the fact that we're also pretty close to the GVWR in our E-350 Chinooks (and that encompasses much more than just the rear axle).

Here is some rear axle code info. The text at the top about 2003/95 was something someone else wrote (I got the chart online). The one outlined in red is the one in my '99 Concourse. It's a full floating axle.

Identify Your Ford Truck Axle From The Door Sticker:

http://www.blueovaltrucks.com/tech-arti ... r-sticker/

The standard setup for an E350 cutaway is/was a Dana 70 HD limited slip with 7400 lb capacity and 4.10 gear ratio (limited slip was an option).

I believe the E450 used a wider Dana 78 (80) with 4.56 ratio.

Does anyone know what modifications Trail Wagon did to the Baja Model to increase the gvwr to 11,200 lbs?

Oh interesting, I didn't know the GVWR on the Baja was higher. On the other hand, it's not the typical E-450 GVWR, so I doubt it's because they went to the E-450 chassis (that's usually 14,400#). I have heard that RV mfgrs can designate new GVWR's officially. I don't know the procedure but I imagine it included some sort of plan presented to Ford or (?) engineers and then approved. I don't know what they actually changed though. Quadvan might know some of it, as they did at least some of the conversions.

On the other hand, that only raises it 500#. So maybe that was just the weight of the new front axle, transfer case, and any larger tires/wheels they used. In that case, perhaps a relatively straightforward procedure with Ford or whomever oversees such official GVWR changes.

Typically Quigley and/or other coversion companies would use a 3 inch lift block under the rear springs to achieve a lift and clear bigger tires, so I don't think they would have used heavier springs. The only difference I see is bigger tires 235x85x16 and the front dana 60. It would be interesting to see if the rear axle load specs changed as well. Anyone have one?

Blue~Go wrote:I don't know how much changing the rear axle/rating would accomplish given the fact that we're also pretty close to the GVWR in our E-350 Chinooks (and that encompasses much more than just the rear axle).

Yes exactly. The gross vehicle mass considerations are largely based on safety, structure, and performance. Balance of mass, brakes, tires, cooling (engine and trans), torque, axle ratio, axle bearing type, hitch design, and a few other chassis-related specs. Even then, in our era of vehicles, the numbers had a lot of flexibility, they were mildly arbitrary, and largely influenced by marketing. If you have a huge load on the rear axle, the load on the front end is reduced and can compromise steering, braking, and stability. I towed a small car on a flat bed trailer with my friend's half ton pickup, it was under the gross and the axle ratings, yet towing was a real handful. Downright scary. So they were a little too generous in their numbers. Just try to be within the numbers and pay close attention to vehicle attitude.

It's more geared toward towing, but the SAE J2807 standard is used in more modern vehicles. There is still some flexibility but it's a far more scientific process than it once was.