Definitely sounds like the notorious gear is broken from it's shaft. I went through this and fixed it last year using the pinning method mentioned in that other thread.

It was easy with a drill press to make the two holes in each of the two gears and then I pressed two automotive roll pins through the two holes using a vice. The key is to get the holes through the two stacked gears as straight as possible and then when you pin them to get the two gears as straight relative to each other as possible. If you spin the gear around in your hand and you see that top broken gear wobbling then you just need to get it straightened out until it doesn't wobble. If you don't get it straight the gear will strain and can kind of catch during parts of it's rotation making the rotation inconsistent and noisy. I think my gear box is still noisier than it was before it broke but it has turned great since then with no problems.

Since I drilled out the rivets to open the gear box I had to use bolts to put it back together and then the nut got in the way of the housing bracket, so I had to cut out a notch on that bracket for it to fit right, it was easy with a Dremel. I then used white lithium grease over all of the gears.

Let me know if you have any questions, I'd be happy to help in any way I can.