E450 wheelbase

I know of OEM 158, 176 wb. Not sure about 206.

Yes it does change depending on length of coach, my E 450 frame was stretched out to accommodate a 32 ft coach and it has 3 drives lines under it.

There should be 2 vin number stickers, one from the factory that says incomplete chassis vin number than another that the RV manufacturer puts on it that say completed manufacturing vin number, that one mat give actual wheel base

Op again. So axle, brake lines possible fuel lines, shock mounts, suspension points all have to be shifted rearward?

They are not exactly shifted on the Ford (or whomever) frame. The Ford frame rails are actually cut in two and a section welded in to lengthen the wheel base to meet the RV manufacturers requirements. The driveshaft in ours is one piece, so probably one made to specs, not a piece welded in. I'm not sure if brake lines and electrical were added to or replaced with longer ones. I haven't noticed any splices in ours, frame rails yes but not other components.
All of this must be done to meet Ford specifications.
Ours does have frame rail extensions behind the rear axle to support the body of the RV and it also does, or can change the towing specs. Ours is still rated to tow 5000lbs but can only have a tongue weight of 350lb.

Ken

Here is Ford's official guidelines for extending the wheelbase:

Ford QVM Q-18R5

All modern coaches will be compliant with that procedure. Prior to the mid-'00s, not all coaches were compliant at the rear frame extensions, resulting in the some reduced towing capacities.

A more likely concern is wether it was extended enough. 206" is great for a 27' coach but not for a 30' coach.

ratio of length to wheel base at 55% is ideal.

A 26 foot with 176 inch wheel base is 56%

Mine is 28'5% with 176 so about 51.6% That leaves me with an over hang of 11.5 feet. Tail swing is huge.

Below 50% an rv becomes much harder to drive with lots of wandering.

I understand the systems affected from a wheel base adjustment are all Ford-supplied or Ford approved. The same goes for GM/Chevy.

- frame filler with extra support
- brake lines
- exhaust pipe
- wiring harness
- drive shaft (ether longer or adding u-joints and more segments)
- parking brake cable
- fuel lines

CLICK HERE to watch a video which includes a section covering a 4 foot wheel base stretch. Unfortunately they don't get into every detail concerning the components.

Ford authorizes specific shops for the wheel base modification. The shops have to follow the Ford-approved process in order for the Ford warranty to be maintained. If a non-Ford approved shop modifies the wheelbase, the warranty is voided, hence motor home manufactures send out their chassis to only Ford-approved shops.

It's a big business modifying the wheelbase. The approved shops have it down to a science. I read a couple of complaints of multi-segmented drive shafts being out of balance which made vibration at higher speeds. They are supposed to be balanced and matched, but a shop can make a mistake like anyone else.

Our chassis has an unmodified 158" wheel base which I find comfort in knowing all systems are "standard". If anything goes wrong in later years, I have a much better chance in finding replacement parts from many more sources.