While driving the other day, all of a sudden the passenger rear window drops. I easily pull it up by hand, but it will not stay up. When I push the window button, I can hear the motor working, but its almost like the window motor gear is spinning freely from the mechanism that raises and lowers the window. Before I tear apart the door panel, can anyone give me any ideas?

You can't avoid tearing into the door panel on this one. Either the window track has fallen from the drive system or you window had fallen from the carrier. Open the door panel and check to see whats going on. You may have to replace the drive motor and gear assembly.

Yep, I know the door panel is coming off, just curious as to whether I need to purchase the whole window regulator assembly or if it is something simple.

what year is the car? If it is an 00+ then the regulators are known for going bad. I believe there is a work around to repair you regulators if it failed in a certain way, otherwise an new regulator is in order. If it is not an 00+, there is not a common problem with them, but we can still help.

you need to buy the regulator. Bought mine from napa for i think 230.00 ish. Came with a new motor.

You don't NEED to buy the regulator, they will just break again, it'* not the regulator motor itself that usually goes, it'* the cheap piece of crap plastic "clip" that holds the cable in place that lifts the window and the "sled". Search window regulator" on this site and you will get a cheap fix that will cost you $0.00- $3.00 maybe + 1-2 hours of your time if you have never done one. There are full instructions with pictures somewhere on the site. Stop suggesting the lazy and expensive fixes for people before looking to see if there is a cheaper fix. Use the wealth of knowledge the veteran users of this site and the car have (I am not one of them but I do kow the cars are fun to drive, fast but pieces of crap all at the same time - why do we still love them - who friggin knows?)

if the whole cable has been eaten by the motor- which usually happens when the clip breaks the whole things needs to be replaced. time to relax

Actually, rarely does the entire cable get "eaten". All 4 of mine went and the cable was always attached to the top portion of the sled, just sitting there. many others explained theirs broke the same way. Point them to the instructions on how to fix themselves with a metal bracket. Search for regulator fix. Used to be posted on the site. Links are dead in some threads though. Costs nothing or next to it. You can also send them out for repair for $50-$75 ea and still tons. Replacements from GM will simply fail again and GM will continue to rape you on the new part. Sometimes only months go by before they fail again.