Bachmann GP35

Below is the diagram. It appears the truck frame "snaps" onto the part with the gears and wheels. Gears and wheels appear to drop down next. Found this at the Bachmann forums.

http://www.bachmanntrains.com/home-usa/dwg/dwgs/11516.pdf

rich

Pry them off

using a small flat screwdriver and start at the end closest to the fuel tank.  This usually pops them right off.  The wheels "snap" into the truck towers and I have found this to be an issue with tracking at times on certain models.  What I do is file off the small nubs that hold the axles in.  This will accomplish 2 things: 1; It will allow the wheels to have some "suspension" per say in that the wheels are free to follow the track contours better, and 2; it will allow for better electrical pickup by allowing the wheels to remain in contact with the rails.  This would be a good time to clean out the gobs of grease they put in at the factory and also clean the wheels of lint, dirt ect!  The wheels should just twist apart.  Re-assemble and gauge the wheels using the NMRA standards gauge!

Hope this helps!

Before

Taking them off, I would check the gage of each set.  Then with the loco on its back, touch power wires to the wheels, one on either side.  When running, you should not see the wheels wobble.  If one does, then it is the problem.  This happens when an engine gets dropped on a hard surface.  Fixing it will depend on the damage.  When I see the problem, I replace the wheel set.  

If it runs without wobble, then it is time to dig deeper.