Whomp, whomp noise under 04 Denali XL; only when cold??

twotoejoe · October 24, 2013

I just purchased an 04 Denali XL with mileage in the mid 90's. It is a 3 owner vehicle in great condition. I purchased it as a replacement for a vehicle that was total lossed in an accident in which I received a broken leg among other injuries. The previous owner brought the car to my house and my daughter test drove it. She said it drove nice with no noises or problems. I looked it over the best I could from my wheelchair and we came to a deal. He delivered it back to me a couple of days later after he had a chance to clean out all of his families belongings and give it a good clean up.

So then my son comes up to spend the weekend last weekend and drives it on Saturday and tells me it is making a 'whomp, whomp' like sound coming from underneath the vehicle. When I pull myself up into it for him to take me for a drive it has mysteriously gone away! He drives it around on a couple of errands the rest of the day and he says it is fine.

Then today my daughter is taking me to therapy and we no more than get out of the driveway than I have her turn the radio off. I hear it start--Whomp, whomp, whomp. Getting louder and faster the more we accerelate. To me, it sounds exactly like an old nylon biased ply tire used to back in the 50's & 60's before they got warmed up; except when she let off the accelerator the sound went away. My therapy is about 3 miles from my house, and it never stopped all the way to the therapy center. After my daughter dropped me off, she went back home. She said it never stopped the entire way back home or back to the therapy center again. Then when we both got back in it to come home, it was still making the same noise. We got within about 200 yards of our home and the noise stopped. We were amazed! So we made a side trip and drove about 5 miles on out the road. No noise either out there or back.

Anyone know what this might be? Like I said, it reminds you of an nylon biased tire when it is cold, or maybe a radial tire with a belt busted. Or maybe a rear axle bearing. BUT it only does it under acceleration and goes away after everything warms up good. Please help!!