Rear Lift gate broken

I have a 2007 Tahoe, and for some reason the rear lift gate will no longer lift on its own. Can anyone tell me how this lift function actually works.
When I press the button for it to open the door, I can hear somthing run inside the liftgate itself. I assume this is unlocking the Lock. Then I can hear the LIft motor engage, but it will suddenly makes a slight clunk sound and stops.
I can manualy open the liftgate by hand and it opens very easy. If I go to close it from the full open position, I can hear the lift motor start but then I hear a slight clunk again and the motor will stop.
I have to assume it has something to do with the lift motor. Anybody have any ideas. Also, does anyone know how to remove the interior rear panel to access the lift motor?

Did you find the problem with your lift gate? Mine is doing the same thing. Any advice would be great

Hey I know this may sound dumb, but check up front and make sure your tailgate switch isn't off. I saw this one day after having my truck for 2 years because I never use it to open the rear hatch, and i switched it off. I got the same results as you get, the motor makes a slight sound, and the gate push open a little, then you have to manually open it, and when you shut it, it grabs and makes another sound locking it. I'm not sure why they give the option of cutting it off, well actually I do, because I've had ish fall out on me from grabbing that handle and not thinking. But try that, if now, you can access the motor on the right side rear panel, I think there are some cover over screws or clips for the door. Not sure, but hope that helps a little.

If the gate switch is off then the motor will not even engage (or at least shouldn't). It sounds like the motor may need replaced

That sucks, my gate wont lock with the rest of the doors.