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Discussion Starter #1
Hi everyone. I have been reading on the forum for a long time. Thanks for all the great things I have learned. We have a 2015 PM 3500. It is a Coachmen Orion RV. It has been very good until a short time ago. When we have it loaded up, sometimes it has a bad wobble that seams to be coming from the rear of the unit. Only does it from 35 to 45 miles per hour when accelerating. Hope somebody has some ideas for me. I did rebalance all the tires. Thanks
 

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Welcome. I am going to assume you did the obvious, check the lug nuts for tightness? Bent rim? Broken cord in one of the rear tires is what I’d guess. Put on a pair of gloves, run your hand around the perimeter if the tire and feel for a slight bulge. Do both rears then roll ahead 3 feet or so and repeat.
 
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I had a bad set of tires on a truck one time I had them rebalanced and check at 2 different shops both said tires were good . I could not for the life of me find the vibrations. the truck had a 2 piece drive shaft so thinking that was the issue I got a new 1 piece alum driveshaft at the tune of $600 and still did nothing changed a few front end parts and still nothing. finally after about a year it was time for new tires and the first drive out of the shop was heaven no more vibration. Just cause the tires balance well and have not visual signs don't mean they are not bad. how old are your tires?
 

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That is another reason to suspect a tire. Rotate them back to front and I’ll bet the vibration goes to the front too.
Best luck.
 

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Discussion Starter #7 (Edited)
Thanks for all the good ideas. I jacked up the rear. I could not wiggle the tires side to side at all. I gave each wheel a spin. Then spin very easy and for a long time. I used a concrete block and set it beside each back wheel. The tires did not move back and forth sideways at all. The rims were also good side to side and up and down. Both rear tire treads have about 3/16" from high to low. I guess they are both out of round. I wonder if this is enough to cause my wobble when accelerating from 35 to 45 mph? The van is smooth the rest of the time. They are too heavy for me to rotate the tires.
 

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Resonance? Worn irregular tire wear. Amplifying under load or no load at 35 to 45 mph? Grab the front cv drive shafts and see if any play.
Feel and look close at your tire tread for irregular wear. Rotate tires as in manual. The front goes straight to the back and the back go to the front but right to left and left to right. My old tires did the same thing at about 60 000km. I have since replaced them.

But I think the proper rotation will be your fix. Take it in if you can not do it but make sure they do the right pattern.
 

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The Original Poster did not reveal which make/model/size his tires are... I had the dreaded tire hop & shimmey on my 2014.

'Road Force Balance' is a newer computerized balancer having a swing arm flywheel-roller that engages after a typical dynamic spin balancing cycle, roller applies 200, 300, 500 pounds force for measuring total eccentric which it translates into a pounds force number to calculate size/location of clip-on lead weights, this number, if below 30, will display a balance solution for the technician to follow that is usually successful.

If you are taking the van in for this service the tires should be full highway running temperatures when they pull the wheels from the vehicle or else the stiffness of the compounds defeats the balance machine which are usually built for lighter tires so that is not so much important with dinky-door passenger tires but for 10-ply E or Euro-C rated commercial tires it really matters.

I found the road force balance is a temporary fix for any tire that can make a 2-ton truck wobble and hop, is only good for a couple thousand miles before rebalancing, at 15,000 miles I replaced the tires and asked the techs to check the ones being removed... Attached is photo of five Vanco Euro C tires with chalked numbers from Road Force measurement: 39, 49, 61, 63 and 19 from the spare. The tire tech said only one, maybe two were balanceable. I'm afraid I put 50,000 miles wear and tear on the suspension & drive shafts in 15,000 miles these tires were being driven on, I finally got sick of the dealerships service writers lying and obstructing my safety concerns so I went with Michelin's...

Find a Tire shop that has the new balancer machines & have them spin them to see what is up.
 

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Discussion Starter #10
Thanks again for all your inputs. I think I will go looking for new tires. I now have Nexen 225 75 16 E rated. 2640 lb. max per tire. This is an RV, so I may look at 245 75 16 E at over 2900 lb/tire. This will give an extra margin. Any tires work better than others? Thanks
 

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Discussion Starter #11
I put new Michelin tires on my ProMaster. The wobble is still there. No change at all. What should I try now to get rid of the wobble?? Thanks
 

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You have gotten us scratching our heads. I’d say wheel out of round or bent. When you lifted them and spun them did you check? Set up a concrete block the tall way beside the wheel and hold a magic marker on it and slowly move it towards the spinning rim right where the rim and the tire meets. Eventually it should touch the spinning wheel and leave a black mark for almost all the wheel and stay consistently along the radius of the wheel. If the line touches only part of the rim or the line moves in and out compared to the rim you found the issue.
Did you try front to back rotation? Alignment usually doesn’t show these symptoms but you may need to try that. Were the old tires scrubbed off on the inside or outside?
 

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The only thing you can realistically do is move tires to different positions to try to isolate which wheel is bad. I had a similar problem which turned out to be a bent rim. A tire shop should find this easily, but two shops missed it in my case. The only other things that cause vibration are cupping due to shocks, and bearing issues which are pretty obvious. Rotor warp can do it, but you would be having braking problems with a rotor that bad.

It's remote, but is it possible its an engine problem being percieved as a tire problem? Easy test: if engine idles smooth, put it in neutral on a downhill at highway speed. Vibration gone, and it's in the drivetrain. Vibration still there and it's in the wheels.
 

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Discussion Starter #14
It only wobbles from 35 to 45 mph when accelerating, never any other time. It can be uphill, downhill, or on the level. It is worst when entering the interstate. Do you think it might be one of the CV joints? I have no other ideas on what to do. It is worse when I have this small camper loaded. I have not had it weighed.
 

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I'm becoming more stumped. Axle/cv issues don't do that, and would be there all the time under all conditions. I'd rule out axles.

Torque converter shudder would do that, but the converter doesnt go to lockup till 6th gear, and what you are describing is more a 4th to 5th gear area. Easy test - try it with the tow haul button engaged. This will delay lockup until deep into 6th.

Remote possibility of an air fuel problem making the engine run rough under certain conditions. Unlikely but possible.

It all leads back to tires and balance. It's laborious, but you could move the spare around to all 4 positions abd see if that affects it. The next step would be to put it on jacks and see if you can reproduce the problem and chase it.
 

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I don’t think you are going to get more help until you have tried the wheel position switch Kip suggests. It has to be ruled out or we are WAGing.
 

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WAGing? Winging a guess? Wearing a gown? Wanting a gelato?
 

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Wild A$$ Guess. You were right! LOL (laugh out..... oh yea you knew that!)
 

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Discussion Starter #19
I tried the tow/haul button. No difference. It wobbles or shakes every time accelerating hard or easy. Only does it from 35 to 45 mph. Never does it when slowing down.
 
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