If you have a Freightliner chassis with passive steer tag axle, or plan on purchasing one, you should review this TSB from Newmar. This highlights certain problems with the design/production of the steer tag axle on Freightliner chassis.
I have a 2017 LADP. The very day (august) I drove this out from the dealer, I noticed the coach was wondering about too much. I called both Newmar and Freitliner and asked the alignment to be checked. Unfortunately, I was not aware of the above TSB or existing problems with the FL tag axles. I listed my issues here on this forum some 3 months later and thats when a couple of helpful people pointed out to me the existing TSB and tag axle problems. Thank you.
So far we have had 5 attempts in dealing with the alignment issues and the problem persists.
After each and every attempt, I was assured by Freightliner, all is well and every thing is within spec!
I have had 8 tires replaced within 8000 mi. the tag sets were replaced twice. (FL must have very good deals from Michelin!).
The coach started having some vibration/shuddering from the rear end in about 4k-5k miles. FL claims it is normal. So I placed a camera behind the tag wheel to see what is going on.
There is a plunger actuated by air valve, one on each side. Once the plungers are extended, they are supposed to keep the tag wheels straight. The plungers extend, when the speed is over 20-25 mph, or when reverse gear is selected, or when the parking brakes are applied.
The plungers retract when speed drops below 20-25mph, or when parked and parking brakes are released and the coach starts moving forward.
The camera was placed behind the passenger side tag wheel. The test consistently highlighted a delay from the driver side retracting the plunger and then a few seconds later the passenger side retracting. Great majority of time, during this delay, the tags started turning to the left, while the coach was tracking straight. In a few cases, it remained straight. The steering of tag occurs likely due to road camber or loading on left rear.
There is also a delay during the time plungers extend. The driver side extends first, then some seconds later the passenger side extends. Perhaps, this is by design. I do not know. However, during plunger retracting, there is clear evidence the tags do steer to the left, even though the coach is tracking straight. I believe this is the reason for slow speed vibration/shuddering I notice. As the tires are dragged and bounce over the road. This will also cause some tire wear over time.
We made two 30 min recording before rain started. Due to clouds, the first recording is a bit difficult to see. The second run we added a flash light which helped.
Run-1, was driving on a state hwy coming to a red light. As the coach slows down to 20-25, you will hear the air release. Then, if you look at the lower left of the video, you will notice the toe link/control arm starts moving to the right and steering the tag to the left, indicating the driver side plunger has retracted. And seconds later the passenger side plunger retracts. Once the coach starts moving, you'll hear the air valve closing. Then the toe link/control arm moves to the left, steering the tag to the right, to center the tag, indicating the driver side has extended. Then seconds later the passenger side plunger extends.