Harmonic Vibrations

[rloechel]

Just finished towing my 2011 Montana Mountaineer 5th wheel RV with my 2008 2500 (6.7) Ram truck. Encountered harmonic vibrations between 50-60 mph, similar to what one experiences when hitting the warning bumps on the side of the highway. Could stop the vibration two ways: 1. By slightly touching the brakes, or 2. by increasing the throttle. The first way stopped the vibrations immediately. The second caused the vibrations to slightly increase, then slowly stop. The Ram has new Michelin tires; the Montana new Goodyear G614s. Do not experience the vibrations when not towing.

Sounds to me like possible tire balancing problems on the RV, but would surely welcome other comments/suggestions.

Any suggestions?

Tks in advance.

Rodger

[waynemoore]

The RV has after market wheels on it. Be sure that the tire place can do luge centric ballancing not all can. Cars and truck with stock wheels have hub centric rims after market do not. That is why you need to find a place that can do luce centric ballancing.

[rohrmann]

You may also want to check the shocks on the truck. If shocks aren't functioning correctly, you can get weird motion with or without a trailer.

[pineranch]

Wheel bearings or tire balance. Harmonics controlled by damping or stiffening the structure. In your case changing the RPM of the offender solved the problem. Run to failure is not an option.

[dieselguy]

Splines dry on drive shaft slip joint if it is 2 piece ... carrier bearing on drive shaft if you have one

[bethandkevin]

quote:Originally posted by dieselguy

Splines dry on drive shaft slip joint if it is 2 piece ... carrier bearing on drive shaft if you have one

dieselguy was much more specific than I was thinking. Many trucks will experience harmonic vibrations when loaded -vs- empty. He offers good advice, it is the first area I would look at.

[pineranch]

Harmonics are much more difficult to trace than resonant frequencys. You didn't say where in the vehicle you felt the vibration. Loaded vs loaded does change the natural frequencies of your vehicle structure so location is important. Once you determine where and when you feel the buzzing, driveshafts and bearings are always a suspect.

[rloechel]

Should have mentioned that the vibration only occured under load at 55-60+/-. Couldn't really tell where the vibrations were coming from. But, it was not from the front end of the truck.

Since the RV tires are new (Goodyear G614), I took the RV back to the dealer to have the tires checked. They found one out of balance. Drove probably 100 miles and only experienced the vibrations one time. Getting truck tire checked next week.

Tks to all for the suggestions!