I have on occasion reamed the center hole of the Kadee centering spring to fit over a slightly oversized center post. The shank of the #5 coupler can also be filed slightly to reduce its thickness if necessary to allow it to move freely in the pocket.
A #11 exacto knife blade and very light pressure while turning will ream out the centering springs to fit better. I have had to do this on some cars. I also have a pair of miniature smooth jaw pliers that holds the spring without mangling it.
Pete.
My suggestion would be to do some careful surgery on the Bachmann draft gear and completely replace it with one of the Kadee boxes. Almost all of my draft gear replacements use screws to hold them in place but a good cement can work in a pinch as a flat car or caboose may not offer enough "meat" to drill and tap into.
The Kadee "Snap Together" box is a good solution for something like a flat car as it doesn't have the molded mounting "ears" that the traditional #232 has.
https://www.kadee.com/media/documents/242ins.pdf
Good Luck, Ed
gmpullmanMy suggestion would be to do some careful surgery on the Bachmann draft gear and completely replace it with one of the Kadee boxes.
I completely agree. I use genuine Kadee coupler boxes over 95% of the time, and the improvement is always worth it.
Wheels, couplers, and track always need to be perfect. Kadee couplers always work properly in Kadee boxes.
-Kevin
Living the dream.