little tip to cure wobbling GP 50 / 40 and U36B and the like

[seadowns]

Hi!
Those locos usually have the traction wheels on the very last axle in the rear truck. I don't know why but that causes the wobbling of some of my older Bachmann diesels.
I cured this issue by exchanging the two rear wheelsets and, like magic, the wobble is over and the locos run with no wiggle and wobble.
The new situated traction tired wheels are doing their job as well, no change in pulling  power.
This improvement is easily done and I am asking why Bachm. is placing the wheels this way, or does no qc check that before?
Hope this little tip will help some of you fellas out there....

Regards
Mathi