Odd Vibration MC8 45-55mph

[chev49]

Hope you checked the pinion  torque as mentioned above when you checked the u joints. I fixed one about 10 yrs ago that had a similar vibration and that was the problem, after disconnecting drive shaft to check the u joints.

[txjeff]

You mentioned that the drive line was repaired twice. One easy thing to check would be if the drive shaft is in time. Make sure both ends of the drive shaft are aligned in the same position.

jeff

[Len Silva]

Any chance you can get it up on a chassis dyno?  That would seem well worth a couple hundred bucks rather that having to road test after every thing you try.

[lostagain]

Txjeff makes a good point I had forgotten about. It happened to me on the D3 2 or 3 years ago when I installed a new drive shaft and Ujoints not properly. I had a vibration. It was pointed out on this board how it should be timed in line. I fixed it by aligning both Ujoints the same and the vibration went away.

JC

[Melbo]

I do not know how to check the pinion torque --- That information would be helpful.

It seems like the consensus is to remove the driveline to check the universal joints.

I will drop the driveline tomorrow and check the to be sure there is nothing amiss.

I was also told to check that the flanges mate solidly and smoothly to each other so I will also check that.

Rocky Mountain Cummins has a shop with a dyno about 6 blocks from my bus I may also check with them first to see what the procedure and cost is.

Thanks for all the ideas and opinions.

Melbo

[Melbo]

I spoke with the service manager at Cummins -- His thoughts were that it would be one of two things (neither of which he was sure he could duplicate on the dyno).

1. Transmission shudder (he was not sure a ZF would do it) he said it was not uncommon for an Allison to do it at that speed.

2. A subtle misalignment of the driveline caused by the torque, air suspension, and weight of the coach under acceleration.

He said that typically bad u joints vibrate more under deceleration -- he discounted the idea of tires being a problem.

He told me to remove all the pressure from the driveline and check it while in place when I lube it up  -- be sure everything is secure and in place.

Once again I appreciate all the thoughts and ideas of how to procede on this.

Melbo

[bevans6]

FWIW and probably not relevant to this particular bus - not all driveshafts are properly timed with the u-joints in phase.  My MC-5 driveshaft has the U-joints about 30 degrees out of phase, the the splines are such that you cannot put it together any other way.

Brian

[Oregonconversion]

Sounds to me like it might be a wheel bearing?

[luvrbus]

Mel, I was talking to Bill at Southern Plains Cummins and was telling him about your problem he said when you check all drive train components and still have the problem he suggested you change the harmonic balancer  if hasn't been changed in the last 100,000 miles he told me those need replacing on a L 10 every 100,000 miles they do it more often on the CNG engines or they shake apart 

good luck

[Melbo]

Well I think I found the problem on the inside drive tire.

Here is a picture of it -- looks like it could cause some subtle vibration --

Don't have the time to do anything with it before we are on the road

I would have not noticed it but I spun the tires getting up on the blocks and it showed the irregular pattern because it was polished up a bit.

The drive line is good (glad I checked it --- thanks for the encouragement) -- Adjusted the brakes -- lubed things up and changed the fuel filters -- so I guess I am ready for the second road trip of the year.

Going to spend some serious time in the bus this trip so I am looking forward to it.

Thanks again for all the input --- good to feel confident as we hit the road.

Melbo

[luvrbus]

Keep the right air pressure in those tires and they won't cup  Melbo I found that out the hard way lol

good luck

[Melbo]

Will do Clifford I will air them all and check my monitors to be sure that they are working properly.

Melbo

[luvrbus]

Yep Mel that is the reason I air tires to max 1st when looking for a vibration if it is a tire problem air pressure will change it then go from there