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H3 making clunking and popping sounds

My 2007, H3 is making a clunking noise when i go from coasting to acceleration. This started after i had the transmission replaced 6months ago. The dealership replaced the transmission and i did not make it the 100 miles to my home from the dealership before the new transmission malfunctioned and my check engine light also came on. It was towed back to the dealership and the new trans was repaired. I was told a magnete had gotten lodged into a gear box?. A week after the truck was vibrating badly, i took it back and the head had to be replaced all this was 15000miles back. Since then it started the clunking noise, the dealership said they could not hear it when they drove it and assured me nothing was wrong. I hear it and anyone that rides with me hears the noise. It is also making a roaring/idled up sound until the trans shifts out of first gear. When i put on the brakes i can hear and feel a small sound like a joint popping. Has anyone had any of these problems?

an 07 anything needing a transmission replaced seems fishy to me. Why was it replaced in the first place? how many miles on the truck? What was the code that the CEL gave you?

Sounds like a universal joint to me. But I have never worked on a Hummer.

The Hummer H3 is actually just a glorified Chevrolet Colorado/GMC Canyon, in essence.
Take the chassis and most of the running gear of those vehicles, upgrade its 4WD system somewhat, add an un-aerodynamic body, and you have the basic concept of the H3. So, even if you haven’t worked on an H3 specifically, you may well be familiar with the mechanic design of it.

That being said, while these vehicles–overall–have a mediocre reliability record, their transmissions are not one of the problem areas.

The clunking noise could indeed be a bad u-joint in the driveshaft, but that possibility doesn’t explain the other symptoms that include what sounds like high revs (possible slippage?) in 1st gear. Even if the vehicle is still under warranty, I would suggest having the trans checked by an independent transmission shop. While it is on the lift, they can check the u-joints also.

DO NOT take it to AAMCO, Lee Myles, Cottman, Mr. Transmission, or other chain operations, as you would likely drive out of those places with more problems than when you drove in.