Vibration Mystery

[benford]

On a passenger vehicle the flex plate can cause this, I don't know what these big RVs have (flywheel/flexplate)
When a flex plate developes a crack they can vibrate under load
just a thought, hope you get it figured out

[bneukam]

I agree with Rich on the ride height. Verify you have the right measurements. You could easily raise, or lower the front 1/4" and see if it changes the vibration. As this will slightly change the angle on the driveline.
Brett

[Jerry]

I have experimented with the ride height approximately a 1/4" either way and it has not affected the vibration. It was one of the first things I done after getting back home as I had a vibration (constant one) after a shop replaced my rear air springs. They had changed the ride height afterwards because "it did not look right" after air spring change. I reset it to specs and the vibration went away.

[birdhunter]

I don't know whether you have different tire sizes front and back but if you don't I would try switching the tires around and see if it makes any difference.

Rich 2002 Magna

[mlgunn]

My 06 Inspire would surge going up small rises when under cruising speed. It seems the transmission was searching between gears. I already had a chip installed and put it on the first level and the surging stopped. Just needed a few extra hp

[Unplanned Tourist]

The frequency of the vibration is the secret. Once you know and can tell that, it's pretty much straight forward process of elimination. Trying to duplicate the vibration at the same speed in different gears will eliminate either from transmission output back or forward. If the frequency changes, it is engine or transmission. If it stays the same, it's driveline, differential or wheel bearing.
Good luck and Happy Glamping.

[Jerry]

Yep...what chaps me is that I sold an excellent H.D. truck chassis vibration analyzer when we downsized to a smaller home. Seems like every time I let an item go, I need it shortly thereafter. I purchased a lot of similar tools years ago, then moved into management and packed them away. I have checked with numerous truck shops around the D/FW area and none have such an analyzer.
Jerry

[mfire1339]

The shop that said #4 cylinder was not performing just missed which cyl was not performing when pressed.








Mike

[Unplanned Tourist]

Originally Posted by Jerry

Yep...what chaps me is that I sold an excellent H.D. truck chassis vibration analyzer when we downsized to a smaller home. Seems like every time I let an item go, I need it shortly thereafter. Jerry

Isn't that the way it seems to go! I guess I'm just fortunate to be able to pick up vibration frequencies by the seat of my pants or something. I did a lot of test driving the customers trucks finding problems over the years. Maybe it's because I'm half deaf, and the other senses kick it up a notch.
Have you tried travelling at one speed and duplicating the vibration in different gears? That may help find your problem.
Also, stop after a long hard pull with the vibration happening for a while and feel the temps of things like u-joints, diffs, steady bearings, or anything that is turning.
Happy Glamping.

[cfowler55]

A single cylinder misfire will cause a vibration frequency of 1/2 engine rpm. A drivetrain vibration is typically higher frequency. If more of a fast chatter could be caused by a torque convertor. Chatter on accel and curves could be diff clutches or degraded friction modifier in diff. Driveshaft vibrations are usually more of a seat of the pants buzz sensation.

[Jerry]

On a scale of 1 to 10, the vibration is about a "2" when it comes in. On rare occasions, it has hit a 5 to a 6. It is definitely coming from the engine, transmission, driveshaft area. When the Cat technician was riding with me, he walked to the rear of the coach and said it was more pronounced there than in the front. He first thought it sounded like the exhaust system was making contact with the frame but, back at the shop, he could not find anything.
Jerry

[Hey Vern]

One thing it may be is the "Flex Plate" from the crankshaft hub to torque converter. These plates have a problem cracking and causing vibrations under load. I have repaired quite a few for this same problem. Sometimes you can inspect without removing transmission through the inspection cover with a flashlight.

[Jerry]

Thanks for that suggestion, Hey Vern! I will get that checked out.
Jerry