I get an odd vibration when accelerating from about 40 to 50 or so. I was thinking it might be front wheel bearings but it doesn't show up consistently so I am a little lost.
I haven't noticed it at all when coasting or maintaining a constant speed just when I'm accelerating and then only in the speed range mentioned.
I would rather fix something when I'm home than when I'm on the road -- called good judgement I think.
Any opinions (I know I'm taking a chance with that) YES ANY opinions appreciated.
Thanks
Melbo
P.S. I am hitting the road again soon ;D
I am sure it could be 100 differant things but the only vibration I ever had like that was my drive shaft bolts were coming loose. give us more info. do you fell it in tour steering wheel, seat or in the structure of the whole bus.
My first thought was also u joints. :)
The driveline is fine --- Was just lubed and checked before the last road trip and nothing was amiss --- it really isn't something that a passenger would notice -- I can feel it in the steering wheel -- the front wheels were balanced when I put the new tires on somewhere less than 7 thousand miles ago.
The drives all have balancing powder
I hope this helps --- I also freshly lubed all the suspension about 2500 miles ago
Melbo
Check to see if you thru off a front balance weight, steering wheel vibration especially at that speed usually indicates a front wheel or
loose front end part.(at least in the automotive world). Same difference just bigger stuff !!
THanks ED
happens only when accelerating at certain speed diffidently something in the power train,Jim had that problem and his was caused by the ring gear bolts coming loose on the cage hope that is not your problem
good luck
The bus was parked for over six months before this last trip --- is it possible that the tire or tires developed a flat spot??
Something loose in the diff does not sound good --- how would that be checked??
Melbo
Does it do it also after you have been driving a while? Tires can get out of round just sitting for long periods, but recover when they get hot again. Anyway, after giving everything a good shake, re-balancing may be worth a try.
can you feel the speed of the vibration? example wheel speed, drive shaft speed, engine speed. can you change gears? Does that change the speed of vibration
Rick 74 Mc-8
Mel, if you think it might be the tires up the pressure to close to max and see if that changes the range of the vibration but doing only on acceleration sounds to me like something does not like that torque range could be a rear wheel bearing going bad,and about the only way you can really check the U joints on 1 is pull the shaft and remove the caps they will be tight as a drum and be wore out
good luck
After driving for a while, feel the wheel bearings with your hand. A bad bearing will be hotter than the others.
JC
How did you check the u-joints? The only way I trust is to disconnect the u-joint and work it through it's full range of movement. I'm guessing you have a seized u-joint that you can feel when the acceleration torque changes the drive train alignment; below 40 mph its not turning fast enough for you to feel and above 50 mph you don't have the torque to cause enough misalignment.
Two things come to mind also. Definately check those u joints disconnected but also check your rear housing pinion bushing and also the tranny bushing for looseness. I had a similar problem in a pickup and it turned out to be the tranny bushing. later
Quote from: Melbo on August 21, 2011, 09:31:54 PM
The bus was parked for over six months before this last trip --- is it possible that the tire or tires developed a flat spot??
Something loose in the diff does not sound good --- how would that be checked??
Melbo
I am replacing to tires right now as a result of flatspots. I only felt the vibration at medium range speeds. When I got up to 60 I couldn't feel it. 45 to 50 I could feel it. Especially on the first black top road leaving home. It was as if the tired heated up and it calmed it down a little.
Ok I looked up the invoice for the drive line and the slip yoke was built and balanced 8/28/2008
It has been lubed five times since it was installed --- I'm wondering if the heat gun would tell me if there is a problem.
I will be adjusting brakes and lubing it up before I hit the road so here is my plan.
I am going to air up the tires (per Clifford) --- Adjust the brakes and lube it up. Check the oil level in the front hubs and tags. The bolts that hold the driveline in place are one use bolts so I don't really want to drop it but if the consensus is that it must be done I will do it.
Then when I am on the road I will check the temps of the hubs on the steers and tags the drive hubs and the temps of the universal joints in the drive line when I get about 50 or 60 miles down the road.
This has bugged me for a long time --- I have jacked the bus up and run each side off the ground to see if it was wheel bearings. I have replaced the tires with michelins. I have had the diff gear set replaced. I have replaced the driveline TWICE the second time is referenced above. The bus is MUCH better than when I started. It is quiet and pleasant to drive but I don't want problems on the road so this odd vibration means something and I would like to find and fix it.
Melbo
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.
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
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.
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
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
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
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
Sounds to me like it might be a wheel bearing?
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
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
Keep the right air pressure in those tires and they won't cup Melbo I found that out the hard way lol
good luck
Will do Clifford I will air them all and check my monitors to be sure that they are working properly.
Melbo
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