That's a good point about heavy rear/light front possibly being part of the problem. I don't experience wandering any more than I have with any normal Ford van (meaning, it's not rack-and-pinion, but without that expectation it's fine). But that said, I'm not "light" in the front and I am relatively light in the rear (under rear axle weight rating even!
).
A couple of thoughts that may or may not apply:
1) I moved my spare to the front. For me it was because taking the ~200+# off the rear axle was a goal because I'm adding 550# to the rear axle when towing, via tongue weight. Even still, I'm under rear axle weight rating when towing now. Moving the spare to the front also adds around 125-150# to teh front axle (I forget the exact number at the moment, but you get the idea). It's very rare that the front axle would ever be overloaded in a gas chassis with our design.
SMan wrote:
IMO The E350 chassis, where adequate for many applications, has a couple of shortcomings in both suspension and brake size.
2) Agreed on the brakes. I had a 2014 take-off front end put on my '99 for this reason. The brakes are MUCH more massive (main reason for mod), but the updated (in 2009) front end suspension can't hurt. It's still Ford's somewhat idiosyncratic design, but somewhat improved.
3) Although this doesn't directly affect wandering, I was VERY happy after putting a set of beefier-than-stock anti-sway bars on my last car; so I couldn't wait to do the same on the Chinook. I LOVE the improvement in the handling, although it's more about staying "tight and level" in the corners. Makes it so much more fun to drive. I went with the big Roadmaster bar in the front, and a stock E-450 bar in the rear (which is somewhere between the stock diameter and the Roadmaster diameter). I found that the Roadmaster bar made the rear ride too jarring -- maybe that would not have been the case if I was overweight on the rear axle (?). The E-450 bar is a compromise between fun/level cornering and non-harsh rear ride over bumps.
4) I did also add a Safe-T-Steer to the front but that was kind of at the bottom of my list as not super necessary. But I was there, it was available, and so I did. What I found was the the recommended size made the rig run straight as an arrow on the highway, but it was a chore to drive on twisty roads or in town (too much wanting to go straight that I had to fight with my arms and the steering wheel in turns). Again, maybe a rig that wandered more would find it just right. Instead I went with a smaller size (IIRC it was meant for a Toyota Dolphin - it's about half as "strong" as the recommended one). What I think would be perfect would be a 3/4 strength one, but at least as of fall 2014 they were not making one (although the place that I did the work with said that they had had more than a few requests for such a size and were recommending that Safe-T-Steer start making one -- not sure if anything ever came of that.
5) There is one more thing that was mentioned, although in the context of that I didn't need it. But if you have "rear wheel steer" at all (rear wander), then there is a track bar you can add (aka pan hard rod). It's a bar that goes diagonally from the rear axle to a solid member to keep the rear axle in line.
Not sure if any of these directly apply to your wander, but figured I'd mention them (now that I think about it this thread is fairly mature and I may already have said all this... if so... never mind!).
I do know that I wouldn't want to just accept it: These Chinooks are just too fun to drive when they are "tuned up" (in the context of an RV anyway).