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tevake · 01-22-2014, 03:11 AM

A little off topic here, but I'm trying to chase down a vibration in my 345 motorhome. At the chassis/steering repair shop yesterday I was told to get rid if the centramatics as they bring a variable into the system that is a potential problem.

So what say, are they helpful. Are they still being used? Can they cause ballance problems? Should I take them off the wheels?

Thanks Richard

jdalrymple · 01-22-2014, 05:27 AM

Quote:

Originally Posted by tevake

A little off topic here, but I'm trying to chase down a vibration in my 345 motorhome. At the chassis/steering repair shop yesterday I was told to get rid if the centramatics as they bring a variable into the system that is a potential problem.

So what say, are they helpful. Are they still being used? Can they cause ballance problems? Should I take them off the wheels?

Thanks Richard

I guess my first questions would be:

Did you remove them? And, If so, did it change any thing?

I put them on my trailer when the trailer was brand new, and after 35K, I have no popped rivets, no cabinets off the walls, and no cracked skins.

Best Regards,

JD

tevake · 01-22-2014, 05:43 AM

The response I got from the shop about taking them off of the Moho was just yesterday. And I am hoping to replace the front the tires today. And have the others ballanced, So that is why I am trying to get clear about the performance of the centramatics. And any problem they may cause.

Inland RV Center, In · 01-22-2014, 05:57 AM

Quote:

Originally Posted by tevake

The response I got from the shop about taking them off of the Moho was just yesterday. And I am hoping to replace the front the tires today. And have the others ballanced, So that is why I am trying to get clear about the performance of the centramatics. And any problem they may cause.

The Centramatics cause a HUGE problem, that has 2 sides.

It reduces the money an owner pays out for repairs for many issues caused by vibration.

That huge problem, is for repair shops, and the super good side is for the owner.

Andy

Silver Goose · 01-22-2014, 06:11 AM

Quote:

Originally Posted by tevake

A little off topic here, but I'm trying to chase down a vibration in my 345 motorhome. At the chassis/steering repair shop yesterday I was told to get rid if the centramatics as they bring a variable into the system that is a potential problem.

So what say, are they helpful. Are they still being used? Can they cause ballance problems? Should I take them off the wheels?

Thanks Richard

I don't believe the Centramatics will cause a balance problem, but they can mask the cause of the problem. If for example they were trying to balance the running gear, it would be nearly impossible to get it right as the Centramatics would be doing its own thing. The correct way is to remove them, diagnose the problem and then make adjustments. Once they get it right, then it would be appropriate to reinstall them.

dznf0g · 01-22-2014, 06:13 AM

I think they are saying to remove then and see if there is a change....ie. eliminate them as a possibility. The only real failure mode of a centramatic is loss of it's oil. Then, I suppose, over time, the balls could stick or wear the tube....but I doubt they are your issue.

tevake · 01-22-2014, 06:46 AM

Thanks Rich, and Silvergoose! So it is true what they say about great minds thinking alike :-)
The Tech I was dealing with seem quite skeptical of them in general.

I like your thinking of sorting any issues then reinstall, thanks

The ballance issue that I'm trying to fix is strangely intermittent, it can start to be noticeable around 40mph. Then peaks around.55, and usually smooths out a bit above 65. So it is not easy to avoid.

Funny tho it was almost constant on the drive from Quartzsite to Phoenix on Monday, then almost completely smooth running on the way to the shop yesterday. Do you think that is the centramatics working to bring them into ballance? I'll admit to being befuddled, so thanks again for the input.

dznf0g · 01-22-2014, 06:59 AM

What MOHO do you have. If it is on the Chev P-chassis, I would start with the bellcranks. A common issue with them. Then I would verify all the steering components have no excessive wear. Then move to bearing condition and adjustment. Then move to wheel balance and/or tire condition.

tevake · 01-22-2014, 07:20 AM

This is on my new to me 1989 , 345le classic. Went thru the steering yesterday. Replaced the left idler arm and the drag link from the steering box to the idler arm. The bell cranks are the blue upgraded ones and are in good shape.

The vibrations are from the back of the coach. I can see that the carrier barrings on the driveshaft are a little tired so that could be some of the issue. Having it dropped and ballanced on Thursday.
But I also see that one wheel on the right rear has a ton of ballance weights on it, so I'm wondering if some of the problem could be there.

At any rate caring for this type of vichicle is new to me, so I do appreciate any knowledgable input.

Silver Goose · 01-22-2014, 08:24 AM

An experienced mechanic understands speed related vibrations. Vibrations that come and go are also not unusual. Anything that rotates can impart a vibration if not balanced. We most often think of tires and wheels, but brake drums and drive shafts factor in as well. One or more tires can be out of round, have a slipped belt or other defect that may not be visible with the vehicle sitting on the ground. Worn suspension parts probably won't cause a vibration but will allow one to become more noticeable. Bearings and bushings wear over time and sometimes get neglected until they fail, often at the least opportune time. There are plenty of things to look at. Good mechanics charge a lot, but in the long run can save you the most money.

Silver Goose · 01-22-2014, 08:45 AM

Vibrations that come and go are often caused by 2 or more issues. An example would be 2 tires on opposite sides that are each slightly out of round. If the high spots were in sync, the vibration may be minimal if not soaked up by the suspension. As you drive around a curve, the outer tire has to travel further than its mate. At some point the high spots are 180° apart and that end of the vehicle would attempt to do a hula dance. As you proceed down the road, the high spots will come back to a point where the vibration diminishes. This is only an example of why some of these things seem to come and go.

**Action** · 01-23-2014, 04:04 PM

Other items that could cause rear vehicle vibration might be -

Balance weights on the driveline - have they come off?
Driveline angle
Rubber bushings on suspension parts causing metal to metal contact.
Suggestion to eliminate the driveline. Operate the vehicle and get it to the high side of the speed range that the vibration occurs. Take your foot off the accelerator and move the shifter to neutral. Does it still vibrate?
IF SO you are NOT looking at driveline issues as they are not involved in a power train that is in neutral. You would want to look at tires, wheels and wheel bearing.
IF NO vibration felt then leave the tire/wheel assembly alone and start look at other issues noted above.

>>>>>>>>>>>Action

DA TAZ · 01-23-2014, 04:53 PM

If you shift to netral the driveshaft is still driven by the axle and is still speed proporshonal it may change but eill still be there. BEST TO REMOVE AND BALANCE. CHECK THE CARRIER BEARING FRIST SLOPPY U JOINTS CAUSE VIBS TOO!

**Action** · 01-23-2014, 06:32 PM

When shifting into neutral the driveline (Including the axle shafts ring & pinion) are no longer under a torsional load. They are just spinning with very, very little load as compared to when powered by the engine. If the driveshaft were out of balance the vibration would seem to go away as the tire to road noise would be much greater than any unloaded driveline issue.

>>>>>>>>>>>>>Action

DA TAZ · 01-23-2014, 08:21 PM

True but rotating mass that is out of balance will still produce vibrations and without torshional loading would most likely be worse --- that is why i said it would change ---- im speaking from experiance being a powertrain engineer with Eaton torque control products

87MH · 01-24-2014, 06:35 AM

Quote:

Originally Posted by DA TAZ

True but rotating mass that is out of balance will still produce vibrations and without torshional loading would most likely be worse --- that is why i said it would change ---- im speaking from experiance being a powertrain engineer with Eaton torque control products

Experience and opinions from experts always appreciated.

Another item to check...look closely at the mounting area of the tag axle/frame interface.

There may well be cracks in either the frame or the tag axle mounting plate where the bolts that mount the two together are located.

This condition is brought on by an attempt (tag axle) to make the P-3X chassis/frame do more than it was designed to do.

**Action** · 01-24-2014, 08:16 AM

My experience is from actual vehicles in the field working at Ford Motor Company and several FLM Dealerships. Out of balance drivelines or out of round ring-pinion gear sets were never felt in the driver's seat at speed when the transmission was in neutral. Not to say the issue isn't there, it is just the forces applied did not create the vibrations to be felt. It is an EZ way to start eliminating systems without extensive dissassembly and measurements.

And as noted above all mounting points are areas to consider, for being too loose, too tight and bound up or fastened in such a way as to create interferance when torque is applied at speed.

>>>>>>>>>>>>>Action

DA TAZ · 01-24-2014, 08:18 AM

Also pay attention to the sway bar, spring, and track bar bushings.

DA TAZ · 01-24-2014, 08:22 AM

See we do think alike

tevake · 01-24-2014, 10:29 AM

Well the chase for the vibration continues. In another direction now.

The work at the tire shop, balancing all wheels. One of the drive wheels had way too much weight of it, and a couple of others need a little tweaking too.
Traded out an inner drive wheel. It has a bit of wobble.
Also replaced the spare tire, which appeared to be original to the coach and with the sticker still on the tread area. So it had never been on the ground. But still very cracked on the side wall. Even after spending its life in the cover. I guess it's caused by heat as well as UV.

I did end up keeping the centramatics installed. They seem to be in good working condition. And with the strong consensus here about their effectiveness.
I decided to disregard the opinion of the Tech at the suspension/ steering repair shop.

After the wheel balancing efforts, the biggest tire bouncing, cabinet rattling vibration is all but gone, so much better in fact that I cancelled the appointment at the driveshaft shop for yesterday and headed back up to the Prescott area.

As was mentioned earlier here a vibration can have more than one cause. Now that the big one is cleared up and I have had some time behind the wheel in a variety of conditions. It clear that more effort is need, there is a smaller tho very insistent quick chattery vibration which is centered in the coach.
While at the chassis shop they said that there is a run out problem at the rear of the drive shaft. Plus one of the carrier bearing surround is looking a bit tired.

I did try the suggested coasting in neutral to check how that would effect the vibration and it did lighten up but didn't go away completely.

So I guess the next step is to drop the shaft assembly and get it looked over and balanced. I will report back after to let you all know how that plays out

Thanks for all the suggestions and insight.

Cheers Richard