mystery vibration?

[mrbee]

I have a 2001 international 3800- dt466 250,000 miles. I've had the rear axle changed from a 5.38 40 spline to a 4.44 36 spline axles. I've only had it about a year. It had a horrible vibration, so we had new steer tires installed and we also had the king pins replaced. While it is a lot better when it comes to vibration, there is still a mystery vibration, bounce, shake around 63-68 miles per hour (according to my GPS). Run it up to about 70-73 and it does okay. In comparison it my old bus, it's horrible. But I also never ran my old bus over 60ish. It had Dayton wheels, this one has budds. Unfortunately, Ive had three different shops do all my work. One for the rear. One for the tires, and one for the king pins. I took the bus back to the king pin people (very respected repair center) and they can feel it but have been unable to narrow down an exact cause. They recommended I have ALL tires spun balanced. Something about the "inner dual" being "off" when they ran it on jack stands. Anyone else experience this type of issue?

[jazty]

Has anyone checked out the u-joints? A u-joint with the needle bearings missing will rattle ya.

[HolyBus]

I second that idea. I had am old car that had work done and everyone madea fuss about marking teh u-joint so it would go back together exactly as removed or it would always vibrate. Check the u-joint that was disconnected when the rear was changed. Replace it if unsure of its condition.

[jazty]

Ah yes! That seems like a likely situation since they did a diff swap. The drive shaft u-joints could be out of sync, or the shaft weights could be turned 180°.

[mrbee]

So I guess a ujoint is something I wouldn't feel all the time? Just at the "sweet spot?" I know he had to swap the yoke from the original assembly cause it was bigger than the replacement. Maybe I should flip the drive shaft 180° and see if that helps. I know before the tires and kingpins, it would bounce like the hood was unlatched. Now it vibrates a good bit but not like it did. Maybe that's just the way it is? Since I don't drive a bus all the time. Maybe its normal? Thanks for the help so far!

[jazty]

No, constant vibration at speed isn't normal. It usually means something is out of true, or broken. I wouldn't go flipping the drive shaft here and there yet. You can take a methodical approach once you know what you're looking for. Read up on u-joints. Make sure the u-joint pairs have correct phasing.


If you're very much unsure then your best bet is to take the bus to a proper driveline shop. They'd be able to look at it and tell you in 2 minutes if something is off. Cheaper way would be to take it back to the folks who did the diff swap and have them look at it...

Here are some related articles:
http://driveshaftvibration.com/drive...ibrationcauses
http://www.hurst-drivelines.com/file...ration-FAQ.pdf
http://www.procarcare.com/includes/c...RIVESHAFT.HTML

[mrbee]

The drive shaft phasing seemed to be correct, so I took it back to the tire shop. After a lecture about not using them for the kingpins, they reluctantly spun balanced tires for me. Turns out the two outer rims on the rear were bent. Installed some new wheels, "match spun," and balanced and they say that should do it. Unfortunately I haven't been able to actually take it up on h interstate due to the weather and work, but we're heading out next week for Florida so I'll keep everyone posted.

[HolyBus]

There are a few of us here in the central FL area. I plan to be between Titusville and Ft. Pierce for Valentine's weekend with my wife to buy a generator and toilet. We are real romantics. We reside just south of Orlando.

[mrbee]

Well we made it to Florida and back. It was a successful trip. Unfortunately, the vibration is still there. It smoothed out around 71 mph so we just drove that speed must of the way. Get around 63-68 and the TV shakes back and forth and the wheelchair lift rattles. What about having the tires "trued?" Is that still done?

[mrbee]

Hit a snow storm on the way home.

[mrbee]

Think it could be my wheel simulators?? I just thought of that.

[nat_ster]

Is the vibration in the rear? or front? What side?

Lift the back axle off the ground and secure the bus well.

Have someone put it in gear and slowly spin the back tires. Put a object on the ground close to the side of the tire. The tire should only be a few inches off the ground. That object is there for your eye to reference distance to.

What your looking for is wheel wobble.

You can check the front tires the same way, just spin by hand.

Now get in the drivers seat and spin them back tires at interstate speed.

Here is what I suspect from reading your posts.

You may have a bent axle on the side that had the bent rims.

A separating tire can also cause massive vibration. The tires that were on the bent rims would be the ones I check first.

I don't think a wheel simulator weighs enough to cause a vibration, but it would not hurt to remove them and see if it helps. What they are good at is holding dirt, snow, ect that causes vibration and RUST.

Nat

[mrbee]

To me, it almost feels like it's coming from the passenger front tire. At least that front hood mirror seems to bounce more and of course I hear the wheel chair lift rattling beside me too. I didn't think of a bent axle. The king pins were bad when I had the rear diff and axles swapped, so the vibration was already there. Once the weather changes and the snow disappears, I'll get her off the ground a check that. I'm almost tempted to take it to a different shop altogether in Columbus or somewhere just to get "fresh" eyes to look at it. Thanks so much for your input!

[nat_ster]

How about the wheel bearing on that passenger front tire? Did you say they checked your steering links?

Nat

[mrbee]

According to my receipt from when the king pins were replaced, all the bearings were inspected and repacked, plus an alignment. I would think when they did the alignment they would have noticed some tie rod issues. Maybe....