Thump in floorboard can’t fine source

[Ponchonutty]

so I’ve been chasing this odd thump when going over unlevel terrian. Mostly seems when the chassis flexes I get what I describe a sound as if someone is hitting the floorboard with a heavy hammer. It doesn’t do this all the time. Mostly when say pulling into a driveway at low speeds. All shocks/struts are new as well as sway bars and endlinks. Anyone else have experience like this? Truck has 185k miles on it and this has been doing this for about the last 10-12k miles

 

[RED TAHOE LS]

Year, Make, Model, 2wd, AWD ?
David g..........

 

[HiHoeSilver]

so I’ve been chasing this odd thump when going over unlevel terrian. Mostly seems when the chassis flexes I get what I describe a sound as if someone is hitting the floorboard with a heavy hammer. It doesn’t do this all the time. Mostly when say pulling into a driveway at low speeds. All shocks/struts are new as well as sway bars and endlinks. Anyone else have experience like this? Truck has 185k miles on it and this has been doing this for about the last 10-12k miles

Check the control arm bushings and ball joints.

 

[Ponchonutty]

Year, Make, Model, 2wd, AWD ?
David g..........

2008 AWD Denali

 

[Ponchonutty]

Check the control arm bushings and ball joints.

I have before but couldn’t find anything. My past experience with ball joints and control arm bushings is you’ll hear it when turning sharp or bumpy roads. This is quiet. Only when you feel the chassis flex is when the thump happens

 

[kbuskill]

Check all your body mounts.

 

[Ponchonutty]

Check all your body mounts.

Yes. This is next plan once the weather is decent so I can pry around. Last visual inspection I didn’t see anything. If they aren’t too much I may just replace them anyways

 

[mtl111]

I'm assuming your truck has torsion bar suspension, if so check the rubber mounts that are inside the brackets at the rear of the torsion bars. I've found these to cause thumping/rattling noises even when they "look" ok. They get worn and allow up and down movement of the torsion bars. Use a prybar to check for any small amount of movement. Let us know what you find, good luck!

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[mikeyss]

I'm assuming your truck has torsion bar suspension, if so check the rubber mounts that are inside the brackets at the rear of the torsion bars. I've found these to cause thumping/rattling noises even when they "look" ok. They get worn and allow up and down movement of the torsion bars. Use a prybar to check for any small amount of movement. Let us know what you find, good luck!

Sent from my SAMSUNG-SM-G930A using Tapatalk

The 07 and up had struts on the front, 2006 is the last year for torsion bars on the 1500's trucks, tahoes and suburbans .

I had a weird noise like that with my older Tahoe, it turned out to be a loose bolt from the transmission mount to the transmission. It didn't appear loose, till one day I was just tightening up every bolt I could see and found it that way

 

[mtl111]

The 07 and up had struts on the front, 2006 is the last year for torsion bars on the 1500's trucks, tahoes and suburbans .

I had a weird noise like that with my older Tahoe, it turned out to be a loose bolt from the transmission mount to the transmission. It didn't appear loose, till one day I was just tightening up every bolt I could see and found it that way

My mistake, there was no year of the vehicle mentioned in the first post and i didn't notice this was in the 07 and up forum. I normally only get notifications for the OBS trucks.

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[Doubeleive]

could be the main support-crossmember under the motor/trans, there was a tsb on the NBS for the same issue, the fix was to replace or swap the bolts around and be sure it was all very tight! mine used to do that and it would drive me crazy, same with the rear torsion bar right behind the rear diff, if that was not tight it would "pop" then it just got so worn out I had to replace it.

 

[Doubeleive]

I also had a issue once with the drivers side lower control arm bolt was loose and had worn a egg shaped hole in the frame, had looked at it 50 times and didn't see it, I ended up welding a big thick washer to the frame which worked out just right because the bolt is plenty long enough

 

[guy from norcal]

I'm going with body mounts also. Rock auto has the best price for them.

 

[gpd4]

Motor mounts?

 

[Warriorpluto]

I'm going with body mounts also. Rock auto has the best price for them.

Hop do you change body mounts

 

[kbuskill]

Hop do you change body mounts

Preferably with a lift, but it can be done with jacks and blocks. The trick is you have to loosen/unbolt ALL the mounts or you won't be able to lift the body high enough off the frame to R&R the mounts.

 

[Ponchonutty]

Well I think my sound is actually coming from the rear trailing arms. I’m going to replace all of them once the parts arrive. One lower came in and I replaced the passenger side with it. It already feels better and haven’t heard the actual pop noise since I replaced it

 

[NGAneer]

I'm getting a similar noise when turning right at low speeds, feels like it's under the driver floor. Ball joints, struts and all sway bar hardware is new. I'll have to roll my windows down next time I find one of those familiar places and see if I can tell front or rear. I'd thought tie rods until now.

 

[Ponchonutty]

Well replaced all rear trailing arms. Uppers and lowers are new. Feels tighter in the rear but noise is still there. I think I may try bodymounts next

 

[rscalfani]

@Doubeleive do you happen to have that TSB for the crossmember?

could be the main support-crossmember under the motor/trans, there was a tsb on the NBS for the same issue, the fix was to replace or swap the bolts around and be sure it was all very tight! mine used to do that and it would drive me crazy, same with the rear torsion bar right behind the rear diff, if that was not tight it would "pop" then it just got so worn out I had to replace it.