What I have to say about these engines isn't good.
I have a set of these same B&M GP9's purchased used about 6 years ago. I had the same issue with stripped gears, replaced them with metal and they still stripped. I've also had electronic issues with them including suddenly reversing direction when passing through switches.
Frankly, I have concluded these engines are junk and not the best purchase I ever made.
On the extremely rare occasions I run these now I do so using a single engine locked in forward on a train of no longer than six cars. That, at least, seems to have stopped the drive gear from stripping and the sudden reversing.
Curt
