Consistent rhythmic thumb from rear, worse when braking

[RJL]

My son drove from out of town with no problems. We got in the car today and immediately heard a loud rhythmic thumping sound from the rear. Almost sounds like it is on both sides in the back, but very hard to tell. It happens in both forward and reverse. It gets much louder when braking. We looked at both brakes and rotors and did not see anything unusual from what we could see. Obviously the faster we go the quicker the thump. We also swapped the tires with the spare to rule out a tire issue. Anybody have anything similar happen or have any thoughts on what it could be?

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[Chiefthepup]

Maybe this might help a bit? Wish I could give u any real help. Keep us updated!

 

[RJL]

Thanks. Fairly certain it is not a bearing based on the rhythmic thumping at all speeds. It odd it was fine last time we drove it and now loud thumping. Very easy to hear but hard to pinpoint side or middle.

 

[Mark S.]

The big clue is the increase in frequency with an increase in speed. That almost certainly means something to do with the tire rotation speed.

You say you changed out the spare to rule out tires, but I’m not conviced you’ve done so (ruled out the tires, that is). What you describe sounds suspiciously like flat spots on the tires. If more than one tire has a flat spot changing one will not eliminate the noise. Another culprit could be loss of tire balance. Did you happen to drive through any mud lately?

 

[scaryhours]

If you go in the back and push on the hatch right below the glass while having someone sit in the car, you’ll hear the noise. It’s caused from wind coming through the rear vents. A poor engineering choice.

 

[Bucko]

My son drove from out of town with no problems. We got in the car today and immediately heard a loud rhythmic thumping sound from the rear. Almost sounds like it is on both sides in the back, but very hard to tell. It happens in both forward and reverse. It gets much louder when braking. We looked at both brakes and rotors and did not see anything unusual from what we could see. Obviously the faster we go the quicker the thump. We also swapped the tires with the spare to rule out a tire issue. Anybody have anything similar happen or have any thoughts on what it could be?

Maybe your son did some spirited driving?

 

[RJL]

He did drive through very heavy rainfall though no mud. I agree with Mark S. That this has something to do with rotation due to it happening at every speed, and it increasing in frequency with speed. I thought it could be a flat spot or a internal delaminating of a tire, which is why we tried the spare on both rear tires. I do not think more than one tire would develop a flat spot at the exact same time, and when I swapped out the spare if there were two tires with flat spots the rhythmic sound would be altered, which did not occur. The odd part is how much louder it becomes when braking, and it sounds more mechanical than thumping with the brakes. But I don’t see an issue with the brakes or rotors, no scarring or anything. I walked alongside the car while he drove and I could here the noise. Wondering if it could be coming from inside the differential, or if it has anything to do with the 4wd system.

 

[Meanderthal]

It would be really great if you could get a recording of the sound. Probably best if you could get both inside and outside recordings, since you can here it walking beside the vehicle. Since it is noticeable at that slow of a speed, I suspect it is not a flat spot on the tire(s). Louder with brakes is a good clue but since it is still there when not applying the brakes, it most likely is not brake related. You are doing a good job of diagnosing but we need more to be of any help.

 

[Mark S.]

Wondering if it could be coming from inside the differential, or if it has anything to do with the 4wd system.

It could be the diff; that also sees a linear increase in rotation as you increase speed. Thumping noises, however, are not typically associated with a differential. Have you looked to see if anything is wrapped around the drive shaft?

 

[RJL]

We did look all under the vehicle to see if we could find anything to explain the noise. I do know that the sound happens in the exact same part of the rotation each time as I was able to walk alongside the vehicle as it drove and the tire stem was in the same spot every time the noise occurred.
But we drove it further today to see if we could narrow down the exact location. After driving a couple miles the sound was dramatically reduced. And no longer did the brakes create a louder sound. I had to ride in the far back of the vehicle and with the AC and radio off I could hear a faint rhythmic thumping at about 15-20 mph. If I was not focused on it I would never even notice it, and you could not hear it from the front row seats. We are guessing whatever issue it has, has probably been there much longer than we realize but never noticed it before. Something must of caused it to be louder after his 4 hour drive here in very heavy rain. It makes me want to think it is brake related and the rain caused a rust build up or something got caught in the mechanism. But that does not make much logical sense, and brake noise issues are more squealing in nature. At a lost to what the underlying cause is and if we should be overly concerned at this point.

 

[Mark S.]

We did look all under the vehicle to see if we could find anything to explain the noise. I do know that the sound happens in the exact same part of the rotation each time as I was able to walk alongside the vehicle as it drove and the tire stem was in the same spot every time the noise occurred.
But we drove it further today to see if we could narrow down the exact location. After driving a couple miles the sound was dramatically reduced. And no longer did the brakes create a louder sound. I had to ride in the far back of the vehicle and with the AC and radio off I could hear a faint rhythmic thumping at about 15-20 mph. If I was not focused on it I would never even notice it, and you could not hear it from the front row seats. We are guessing whatever issue it has, has probably been there much longer than we realize but never noticed it before. Something must of caused it to be louder after his 4 hour drive here in very heavy rain. It makes me want to think it is brake related and the rain caused a rust build up or something got caught in the mechanism. But that does not make much logical sense, and brake noise issues are more squealing in nature. At a lost to what the underlying cause is and if we should be overly concerned at this point.

Very curious too. If the noise gets as bad as you first described again I would absolutely take it in. Even if they can't find anything wrong you need to get this issue documented in case it develops into something requiring a warranty claim.

Please keep us posted as to what you find.

 

[Meanderthal]

We did look all under the vehicle to see if we could find anything to explain the noise. I do know that the sound happens in the exact same part of the rotation each time as I was able to walk alongside the vehicle as it drove and the tire stem was in the same spot every time the noise occurred.
But we drove it further today to see if we could narrow down the exact location. After driving a couple miles the sound was dramatically reduced. And no longer did the brakes create a louder sound. I had to ride in the far back of the vehicle and with the AC and radio off I could hear a faint rhythmic thumping at about 15-20 mph. If I was not focused on it I would never even notice it, and you could not hear it from the front row seats. We are guessing whatever issue it has, has probably been there much longer than we realize but never noticed it before. Something must of caused it to be louder after his 4 hour drive here in very heavy rain. It makes me want to think it is brake related and the rain caused a rust build up or something got caught in the mechanism. But that does not make much logical sense, and brake noise issues are more squealing in nature. At a lost to what the underlying cause is and if we should be overly concerned at this point.

Nice diagnosing with noticing the wheel in the same spot every time the noise was heard. To me that eliminates the differential (almost). Seems like it should be drive axle, brake, wheel bearing, or tire related.

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