I have come across lots of 360's with the tray sticking when trying to eject and having to tap the front of the drive while its trying to eject to get it to spit out the tray. My own tray has been sticking since about 2 months after purchasing the xbox from new (about a year and half). I say it sticks because sometimes it will open on its own like theres nothing wrong.
Since i recently had the 3 rings on my own box, While I had it open I thought I would have a look at the tray and grease it up thinking thats all it needed. When I took the tray off I found that some of the teeth were broken off and this must be where the gears lay when the drive is closed and is the cause for my tray not opening.
The Broken teeth on the underside of my tray
I realise most of us would notice the sound of these teeth breaking and most often I would think the problem is the tray needs greasing, but I thought I would share my fix for reference.
As the teeth had not broken all the way down I thought that I would try to raise the gear that contacts them to see if it could make contact again.
Looking at the drive from the front All you need to do is remove the band then remove the wheel the band goes around by pulling gently like below:
Pull up evenly both sides and it will slide off.
Then the large gear will then slide off easily, the one I needed to raise.
The main Gear
As the gear cups over a pivot point All I needed to do was raise it slightly by shoving something inside the cup before putting back over the point but carefully making sure its not raised too much so other teeth dont make contact. I only needed a small rise of no more than a millimetre. So I used a polishing head out of my dremel kit, and sliced it up to the required size. Its only made out of felt so was easily shaped with a stanley knife.
Felt Polishing Head.
There was enough play in the gear to allow a raise of a couple of mm, before it would rub on the underside of the upper wheel, so there should be no grinding of the wheels making more problems for the future.
I put it all back together and it now opens every time.