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NealH
02-18-2011, 07:39 PM
I am new to Sprinter and this Forum. My company purchased a 2010 Freightliner Sprinter 3500 with a 15' box on the back 2 months ago. Everything with the vehicle operates smoothly until you reach 55 - 60 MPH. At this speed, the front end of the truck begins to bounce. It feels as if there is an unbalanced wheel. It is rhythmic and definitely not a result of road conditions. After 1 week and confirmation by several drivers that the truck has an issue it was returned to the dealer. Over the course of 4 weeks they replaced the driveshaft, swapped all 4 wheels & tires and had multiple discussions with Morgan-Olson who constructs the boxes. When they returned the vihicle it was immediately obvious that the problem presists. Interestingly enough, this afternoon I drove a 2011 Mercedes Sprinter identical to ours and it has the same issue at the same speed. I know many Sprinters are vans but has anything else experienced this with a box truck? Any ideas?:hmmm:

showkey
02-18-2011, 10:39 PM
Does the bounce get worse or better at faster speeds say 70 MPH?

By bounce I suspect you mean chassis movement up and down?

Does the steering wheel vibrate or shimmy?

mackconsult
02-18-2011, 10:56 PM
sounds like a resonance thing .....

autostaretx
02-18-2011, 11:13 PM
If you were near Portland Oregon, you could take it to Upscale Auto (a.k.a. SprinterStore) for their analysis.
See this thread (plus others) http://sprinter-source.com/forum/showthread.php?t=9706

You could test some of the "resonance" theory by putting a significant load (1000 or more pounds) at the front (driver's end) of the box to see if shifting the percentage of weight to the front axle helped.

good luck
--dick

NealH
02-19-2011, 12:10 PM
Does the bounce get worse or better at faster speeds say 70 MPH?

If the truck is driven over 65 it seems to fade away.

By bounce I suspect you mean chassis movement up and down?
Yes- the whole front of the truck. Youc an feel it in the pedal, steering wheel. If you look at the side mirrors they are bouncing up and own as well.

Does the steering wheel vibrate or shimmy?
Vibrates/ bounces up and down. Does not shimmy left or right.

NealH
02-19-2011, 12:13 PM
Thanks. we tried this and it did not have any effect. loaded up or empty it does the same thing between 55 and 60 MPH.

jdcaples
02-19-2011, 03:00 PM
It's not common any more, but shops used to balance wheels and - most importantly, the brake assembly - on the vehicle by hoisting it up and using a machine to spin the wheel at high speed while everything was still bolted to the vehicle.

It was more art than science, but it unveiled systemic (wheel+tire+braking hardware assembly) imbalances. Standard weights, just like today, were used to balance the system of each wheel assembly.

As for the other 3500 doing the same thing, remote as it might be, a lot of defective parts or out of spec assembly may impact each vehicle and causing the same symptom.

I hope you find resolution soon

-Jon

'06 sprinter
02-20-2011, 12:11 PM
i had a nasty bounce like that right out of the dealer on a '10 all 6 tires were flat spotted everymorning they would be like this until 3-4 miles on highway right near my house. i raised the tire pressures to 60 all around and it stopped. i have the continentals looks like a mud and snow tread not sure of the model on them.

sailquik
02-22-2011, 12:50 PM
Jon has a good idea.... try to find some one with an old Alemite "on the vehicle" balancing
machine. It will spin the tire up to speed and the sensor under the suspension will show
them the heavy side.
They add weight on the light side and then "spread" the weights.
There is also the Hamer "3 point" balancing system that uses the Alemite machines.
Some of the really upscale high end tire and alignment shops have more modern versions
of the Alemite equipment and can balance your tires on the vehicle.
I would suspect an out of balance brake rotor may be the cause of this problem.
Not sure what the dealers have done, but they could pull the rotor, bolt it to the
wheel, and balance the assembly.
Hope this helps,
Roger

Paisa
02-22-2011, 04:29 PM
The resolution to resonances is damping. A resonance that persists is usually due to improper or insufficient damping. Shock absorbers are supposed to control damping. However, in vehicles most shocks do most of the damping on the rebound - 60% or more - sometimes up to 100%. When the rebound damping is 100%, then you have a single-action shock absorber. Single-action shocks used to be very common on trucks. Damping on the jounce, in other words, can be from 0% in a single-action shock to usually no more than 40% in street shocks. Rally shocks can sometimes be found where the damping on the jounce equals the damping on the rebound. The original equipment shocks are made by Boge IIRC. The best aftermarket shocks available easily for the Sprinter are made by Koni and are adjustable. However, IIRC only the rebound damping is adjustable. The jounce damping is fixed. If you can afford it, you may want to try installing some Konis and adjust them to the max and see if that helps. If you do that, please let us know what your experience is.

1hen2ducks
02-23-2011, 05:44 AM
Would it be possible that the weight ratio is all wonky front to back ?
What is the working weight of the front tires on a scales as compared to the rear tires?
How much of the van's weight is aft of the center of the wheelbase ? (abaft the beam)
where is the center of gravity when accelerating , when still ?
I'm wondering if the tail is waggin the dog.

Just wondering,
Mike

Eric Experience
02-23-2011, 09:01 AM
Neal.
With a problem like this you should first determin if it is a mechanical problem or a air turbulance problem. The simple way to find this out is to take it out on a windy day and accurately record the speed the vibration starts driving into the wind and with the wind.
If the speed is the same you know it is mechanical. Eric.