Thumping sound from rear at speeds above 60mph

[wfcentral]

Sorry - long story. Lots of info. I will try to be brief.

During the month of May I made six trips to my families home 330 miles away. Each trip was fine and I was able to cruise at 65-70mph with no issues. On the very last trip down there I noticed a sound as I was 1 hr from my destination. It sounded like a shoe in a dryer... thump/thump/thump. Not extremely loud, but non stop and very hard to ignore. It got louder the higher the speed was. I assumed it had something to do with the road surface in that area and the fact I was now towing my car behind. On the final trip home I noticed that the sound now continued ALL THE WAY HOME. So, it was not just that stretch of road. I even removed the tow vehicle 1 hour from home and had my wife drive it just to see if that was the cause/factor. Nope, still the same sound. At 50mph and lower you cannot hear it. At 60mph you can hear it if you listen carefully. At 65mph there is no doubt about a problem and I didn't go faster than that.

This is a 2019 vehicle with 20k miles on it. No accidents. Bought new.

So - I took it to a Truck Center I like so they could do the oil change, wash and take a look at the rear tires. My first thought (and theirs) was that the rear tires were out of balance / threw a weight. I noted there there were no visible weights on the wheels, but there never have been that I could see. It has aluminum wheels and I was told sometimes the weights are mounted to the back side?? The mechanic checked the tires and reported that each tire in the rear was "4 grams out" and needed to be balanced. They did this and test drove it and reported it was fixed. I picked it up at the end of their day and drove it to storage. It is STILL BROKE. Still doing the same thing. I did notice that they put weights on the aluminum rims. So, I find it odd that we have had tire work done at Discount tire on this rig and they never put weights on it.

So, we have a trip coming up next week and a long haul in July. I don't know where to take it next?

My options are to take it to the local RV Dealer Service Department (we aren't crazy about them) who might at least know what an RV is supposed to sound like going down the road. Apparently, the truck center (works on large trucks and rigs) didn't know what they were listening for and I guess as soon as they heard all the racket an RV makes they stopped listening for the problem.

My other option is to take it to Discount tire and have them recheck the tires since the Truck Shop was having several issues while I was there and it's possible they didn't do a good job with the tire balancing. (They broke the plastic hub covers that go in the center of the rear aluminum dual tires [ both sides ], forgot to wash the rig, forgot to put the oil change sticker in the window).

Thoughts anyone?

Also - I did watch several videos on bad bearings and it is not making a humming / growling sound. It is just a whump whump whump sound.

I also tried shifting to neutral when the vehicle was going downhill and the thumping sound was still present. It is in time with the speed of the vehicle. Faster speed = faster thumping.

[TripleGGG]

I've had a loose brake pad make a thumping noise on pickups that the noise would increase as speed increased. Never had that on a motorhome.

[Bill Gail]

Originally Posted by wfcentral

Sorry - long story. Lots of info. I will try to be brief.

During the month of May I made six trips to my families home 330 miles away. Each trip was fine and I was able to cruise at 65-70mph with no issues. On the very last trip down there I noticed a sound as I was 1 hr from my destination. It sounded like a shoe in a dryer... thump/thump/thump. Not extremely loud, but non stop and very hard to ignore. It got louder the higher the speed was. I assumed it had something to do with the road surface in that area and the fact I was now towing my car behind. On the final trip home I noticed that the sound now continued ALL THE WAY HOME. So, it was not just that stretch of road. I even removed the tow vehicle 1 hour from home and had my wife drive it just to see if that was the cause/factor. Nope, still the same sound. At 50mph and lower you cannot hear it. At 60mph you can hear it if you listen carefully. At 65mph there is no doubt about a problem and I didn't go faster than that.

This is a 2019 vehicle with 20k miles on it. No accidents. Bought new.

So - I took it to a Truck Center I like so they could do the oil change, wash and take a look at the rear tires. My first thought (and theirs) was that the rear tires were out of balance / threw a weight. I noted there there were no visible weights on the wheels, but there never have been that I could see. It has aluminum wheels and I was told sometimes the weights are mounted to the back side?? The mechanic checked the tires and reported that each tire in the rear was "4 grams out" and needed to be balanced. They did this and test drove it and reported it was fixed. I picked it up at the end of their day and drove it to storage. It is STILL BROKE. Still doing the same thing. I did notice that they put weights on the aluminum rims. So, I find it odd that we have had tire work done at Discount tire on this rig and they never put weights on it.

So, we have a trip coming up next week and a long haul in July. I don't know where to take it next?

My options are to take it to the local RV Dealer Service Department (we aren't crazy about them) who might at least know what an RV is supposed to sound like going down the road. Apparently, the truck center (works on large trucks and rigs) didn't know what they were listening for and I guess as soon as they heard all the racket an RV makes they stopped listening for the problem.

My other option is to take it to Discount tire and have them recheck the tires since the Truck Shop was having several issues while I was there and it's possible they didn't do a good job with the tire balancing. (They broke the plastic hub covers that go in the center of the rear aluminum dual tires [ both sides ], forgot to wash the rig, forgot to put the oil change sticker in the window).

Thoughts anyone?

Also - I did watch several videos on bad bearings and it is not making a humming / growling sound. It is just a whump whump whump sound.

I also tried shifting to neutral when the vehicle was going downhill and the thumping sound was still present. It is in time with the speed of the vehicle. Faster speed = faster thumping.

I had a similar problem.

Thumping from the rear of the coach got progressively worse over a week of driving . Started out like a stone was stuck in a tire tread , then increased by the end of the week to the point I didn't want to drive it .

Took it in to the shop who installed the tires . They removed the rear duals and found one of the inner duals had a separated belt.

Regarding the Truck Shop damaging and breaking your hub covers . Have they reimbursed you for the damage ? They are responsible .

[Xmcdog]

Sounds like a tire issue. Ply separation most likely.

[Elwood58]

Our aluminum wheels have no weights because they have centramatic beads. I would unmount drive tires for close inspection.

[CRV2]

I had something similar but on my duramax previous tow vehicle, the last shop I took it too raised the rear axle off the ground (secured with chocks in the front and jack stands in the rear) and started the engine and placed the truck in gear (relatively slowly) and showed me that one of the rear tires had a bad belt in it, you could see it very easy with the tire rolling going back and forth. I am not sure if I would do that test on my class c though, perhaps instead have the tires "road force balanced" if you have a shop that offers that, or simply take it to discount tire as you mentioned, they will be happy to find the problem (if it is the tires) and sell you new ones. ~Craig

[wfcentral]

Originally Posted by Bill Gail

I had a similar problem.

Thumping from the rear of the coach got progressively worse over a week of driving . Started out like a stone was stuck in a tire tread , then increased by the end of the week to the point I didn't want to drive it .

Took it in to the shop who installed the tires . They removed the rear duals and found one of the inner duals had a separated belt.

Regarding the Truck Shop damaging and breaking your hub covers . Have they reimbursed you for the damage ? They are responsible .

Yes - when they showed me that they had busted them the first thing he said was "we are going to make this right and will get replacements ordered and installed at no cost... but, it will take 5 days to get them in...."

[jacwjames]

I had a tire break a cord and big bulge was on the tire, I stopped twice to try and find what was wrong. Both times the tire stopped with the bulge on the bottom.

[Dutch Star Don]

It's hard to inspect duals, but as others said, it sound like a tread separation. They often manifest them self visually, as a bulge in the tread or sidewall, or a wavy looking tread. Finding a bulge is hard, unless you get the coach in the air or the tire off. The wave can often be spotted by examining the tread.

Obviously, the tread has a pattern, when looking for a separation, you'll see the pattern widen or get a wave in it. Take some chalk, mark what you can see, inspect for distortion in the tread pattern and then move the coach ahead and inspect the next section.

Here are two photos....the first one, if look closely, has a wave in the tread. The other is an obvious bulge.

[THenne1713]

Crawl under and INSPECT slowly w/ creeper/ FLASHLIGHT, but also check kitchen, bath, storage? Stored tables, chairs? I hit pothole at entrance ramp after pothole at Gas station drive, and had big BANG on ramp that made me pull over and look under... but did not realize until home 1,000-miles (?) later changing GEN OIL that 8-foot of 3-inch tailpipe missing; the hanger peeled the weld off the pipe... may have also been the earlier PINGing that I thought sounded like valve clatter? New PIPE now has x3 wrap-around hangers, so failure of any one does not leave it sagging/ bouncing. LUCK p.s. ALSO CHECK ROOF AND AWNINGS/ ATTACHMENTS?

[twinboat]

Bad tire.
When I got the thump, thump, the tire looked fine, until we let the air out. Then the damage was apparent.

[wfcentral]

I took the RV to Discount Tire yesterday morning. I asked them to check and re-balance the rear four tires. As soon as they removed the left side they saw this problem. So, the job went from check the balance to buying a new tire. After the replacement I did a test drive and the problem is gone - YAY. Can't believe the first shop missed this.

[twinboat]

You can balance a spinning egg, but its still gonna roll funny.

[Dutch Star Don]

I think Stevie Wonder could have spotted that one. Someone sure blew it at the first store. With that said, it may not have been as large of an egg during the first inspection. However, if you carefully look at any tire, you can often see the start of an issue.