2004 Itasca Sunrise Porpoising Problem

[estrang]

I recently purchased a 2004 Itasca Sunrise with Workhorse W22 Chassis. On my first trip I had two issues. 1) Even mild rises on the highways and especially bridges resulted in excessive porpoising. 2) When passed by large units (18 wheelers and large motor homes, it feels like I am being sucked right into their lanes when they initially start to pass.

I read somewhere that this year W22 had these issues and new shocks helped. Can someone verify that is an initial step in fixing my problems. What would help the pulling effect from the larger units?

Thanks in advance.
R/Chuck

[LVRVLUVR]

Originally Posted by estrang

I recently purchased a 2004 Itasca Sunrise with Workhorse W22 Chassis. On my first trip I had two issues. 1) Even mild rises on the highways and especially bridges resulted in excessive porpoising. 2) When passed by large units (18 wheelers and large motor homes, it feels like I am being sucked right into their lanes when they initially start to pass.

I read somewhere that this year W22 had these issues and new shocks helped. Can someone verify that is an initial step in fixing my problems. What would help the pulling effect from the larger units?

Thanks in advance.
R/Chuck

if you go with the new bilstiens,, it will help with that....

suggest you get it weighed first though

[Pekenoe]

New shocks and look into a sway / stabilizer bar for the rear as well for the porpoising. I assume you are not towing a trailer? If you are towing a trailer then equalizer bars will nearly eliminate the problem.

The problem with being sucked into the other lanes stems from the large volumn of air being pushed sideways from the passer and blowing your rear away from them twisting your front towards them... not fun. Again, if towing, an anti sway bar. If not there is not really much you can do, there is some evidence that the application of vortex generators on your trailing edges help. I did talk to a gentleman that had them on his fifth wheel and he did acknowledge that they helped a lot, whether they will help on a single unit not sure. Air tab is one manufacturer, 3m another.

[530ktm]

When you mention porpoising that sounds like your shocks are worn out and perhaps you have too much weight in the back. More details are really needed to try and help with this.

[CLIFFTALL]

Here's a link to previous threads that may assist.

https://www.google.com/search?q=Porp...com&gws_rd=ssl

[ChasA]

Yep, new Bilsteins all around and a really big Helwig anti-sway bar on the rear. You won't believe the difference.

[Clay L]

Even if the shocks are good the ride is bus like and in certain conditions – concrete roads and approaches to and exits from bridges on these roads - you get a large excursion down that can be disconcerting. It rebounds back a little above the zero line and then back to zero. Some people have interpreted this as porpoising but I don’t agree. The suspension does not seem to be under damped but rather is critically damped which is what you want. The large excursion is a result of the engineers trying to give you a bus like ride.
Bilstein or Koni shocks will eliminate the issue but (at least in my case) will result in a rougher ride. At about 50,000 miles I installed the Koni FSD shocks and the ride is terrible. If I knew then what I know now I would have gone with Monroe shocks.

Also if your chassis was made before 9/2/2003 (chassis not motor home - there will be a difference) you will have a 2 inch front stabilizer bar. My motor home is 2004 model year but is built on a 2003 chassis. This is common.

In September of 2003 WH changed to a 2.5 inch bar.
If your chassis has the 2 inch bar I would strongly recommend that you have the 2.5 inch bar installed. I did and it made a huge improvement in roll or side to side sway.

This is from an email I got from WH in 2005:

"The part number for the Front Stabilizer Bar with Brackets is: W0005643.

This bar was found to have an advantage over the original 2" bar, and was
put into regular production on 9/2/2003.

The installation is very straightforward. Remove 4 retaining nuts while
supporting bar, remove bar, hold new bar in position, re-install 4 retaining
nuts, and torque to specification. This procedure is NOT meant to replace
the service manual, but is a generalized procedure.

The upgraded stabilizer bar has been shown to provide the following
benefits:
1. Reduced Body Roll when cornering.
2. Reduced "rocking" when passed by or passing large vehicles.
3. Reduced "rocking" when traversing bumps on an angle."


The installation procedure is below- I did not raise the coach, just crawled under it:

Stabilizer Shaft Replacement (Front) (W20/W22)

Removal Procedure
1. Raise the vehicle on a hoist
2. Remove the nuts and washers from the stabilizer shaft clamp and the right front leaf spring.
3. Remove the nuts and washers from the stabilizer shaft clamp and the left front leaf spring, and remove the stabilizer shaft from the vehicle.
4. Remove the clamps from the stabilizer shaft.
5. Remove the insulators from the stabilizer shaft.

Installation Procedure
1. Install the insulators to the stabilizer shaft.
2. Install the clamps to the stabilizer shaft.

Notice: Refer to Fastener Notice in Cautions and Notices in the WCC Service Manual.

3. Install the washers and nuts to the stabilizer shaft clamp and the left front leaf spring.
4. Install the washers and nuts to the stabilizer shaft clamp and the right front leaf spring.

Tighten the stabilizer shaft clamp nuts to
373 N·m (275 lb ft).
5. Lower the vehicle.

[jauguston]

Koni FSD.

[jauguston]

Koni FSD. Not Bilsteins. Koni cost more and there is a reason.