On this subject matter involving a 2006 2100 built on a 2005 or 2006 E350 Ford chassis, I feel different than the masses. Here is why.
My wife Irene and I own a 2007 PC-2350 built on a 2007 E350 chassis, bought new from PC-USA in 2007. My brother Tom and his wife Darlene bought a 10 year old 21 foot long 1998 Starflyte on a 1998 E350 chassis. Both motor homes have (I should say had) the same issues and deficiencies straight from Ford.
The following applies to every E350 chassis Made Prior To 2008
.Rear Stabilizer Bar
The problem is plain and simple. Ford never installed a rear stabilizer bar on the pre-2008 E350. Unless PC-USA or a previous owner added a rear bar, you don't have one. Also consider that the 2100 has an extremely poor ratio of wheel base to rear overhang. That further amplifies the condition. The majority of RV weight is on the rear axle without a rear stabilizer bar. That is over-ripe for handling problems.
Adding a heavy duty rear stabilizer bar will have a monumental positive impact on handling.Front Stabilizer Bar
The front stabilizer bar in every E150, E250, E350, and E450 in model years prior to 2008, all have the same poor end link design. The ends of the front stabilizer bar pass through rubber grommets in the lower control arms. The rubber grommet openings quickly wear to an oval shape causing excess play, rendering the bar much less effective. Where I volunteer HERE
, I have seen a number of E150s & E250s, and all had worn out oval shaped grommet end links.
Installing a heavy duty front stabilizer bar will eliminate that mounting method so all play will be forever gone. Being that the new bar is heavy duty, it is much more effective as well.
ADDING: Here is a picture of our 2007 E350 with heavy duty front sway bar installed. Note how the end of it at the top of the picture, is mounted with blue poly bushings and end links. Also, note the lower control arm with the original black rubber grommet still in place, used with the original Ford stabilizer bar. That grommet wears quickly becoming oval, then rendering the bar completely ineffective until after the vehicle is leaning by some amount.
I also believe in a good steering stabilizer. We have a Safe-T-Plus and notice it's effectiveness. It helps the driver from compensating when he doesn't have to, and from over-compensating when he needs to.
You who disagree with me will be hitting my [Disagree] button and you are surely entitled to do so as long as Aimee keeps it available. But you'll never see me using that button on anyone here.
As others have mentioned, a good wheel alignment done while as loaded ready to go on a trip, along with proper tire pressure. If either are wrong, that too will negatively effect handling.