Thump Front Drivers side

[f16z28]

So I've been trying to diagnose this thump I've had since I bought my 2007 Yukon XL 6 months ago. From a dead stop or very slow roll, when I accelerate there is a thump that you can hear and feel from what feels like under the front left area of the vehicle. I thought it was a bad ball joint at first but after looking it over and prying on them they wont budge. When I google the problem all the talk is about sounds from the rear. This is for sure from the front. It feels as thought it's lifting weight off the front when I accelerate and when I let off the gas it drops back down with another thump. This does not happen at slow speeds or higher. Only dead stops and crawling under 5 mph. No uneven wear on the tires either. My thoughts are engine/ tranny mount, upper or lower ball joint, body mount, idler arm or other and forward drive shaft. Please help, it's driving me nuts!

 

[OR VietVet]

Sway bar links or frame bushings. How did you check the motor mount. You only stated how you checked the ball joints. Check the driveshaft?

 

[slocaddy]

X2 on the motor mount, I got lucky, mine had just been replaced, but apperantly someone forgot to tighten bolts down. Exact same discription as you

 

[f16z28]

Update- So I got back under it and pryed on everything. I got the drivers side lower ball joint to move some. So I got a new one and will be installing it this weekend. I'll let you know how it turns out

 

[Reester]

Check the body mount on the front drivers side of your vehicle. These actually go out more frequently than expected and have the same symptoms you've described in your OP


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[YukonCrazy]

What about a single thump from the rear from a dead stop with a good amount of pedal?

 

[f16z28]

Update. Just replaced the lower ball joint. Problem is still there. Gonna so the upper next. But the bottom had definite m movement in it so it wasn't a total loss

 

[Scraps66]

I just "fixed" a similar clunk. It was the driver side sway bar link, broken. I had looked a couple times, but because the bushing between the bar and the lower control arm was still in place, it looked as if it wasn't broken. But then I notice the head of the bolt was broken off the bottom. I replaced with a cheap pair of MOOGs from AZ cuzz they had them. But if I did it over, and I may, I'd order a beefier set from RockAuto.

 

[Reester]

I've had the same problem as you for a while now, I had a friend who is a GM technician of 25+ years take a look at it and he said without a doubt it is the body mount. I've already replaced my upper and control arms, sway bar links, and lower ball joints hoping it would have been an easy fix :nope:

One of these days when I have the extra time and cash (they cost ~$60 a pop) I'll change them out and report back.
Good luck!


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[Grebbler]

Check the torsion bar support member that runs under the seats. It floats on rubber mounts at the frame rails and will clunk at slow speeds.