I have an Athearn GP35 BB with a newer Athearn motor, trucks and decoder that makes a loud grinding noise when I increase the throttle full forward. It sounds like it is rubbing on something but I just can’t find where this is coming from. But on the reverse, it is quiet with no noise. It started when I installed a sound decoder that I later fried. I have since replaced the sound decoder with a motor only decoder from Digitrax. I just do not know what this is even after taking the entire engine and trucks off, lubricating the gears and re-installing everything. Any thoughts or suggestions?
JRP
any chance it’s a wire up against the shell or drive train?
Or somewhere in the gear train something’s not quite aligned right so that in One Direction sounds great but meshes improperly the other direction.
Back in the Jurassic when we actually built locomotive kits, we’d have to “break them in” after assembly to get all the gears meshed right to eliminate binds and noises like yours. You’d do that by putting the engine up on blocks and connecting it to power and run it on full throttle for anywhere for a half hour to an hour in each direction. Real railroads did that too in the steam days, after heavy shopping they’d break in their passenger engines on a few freights before putting them in passenger service.
Try raising your engine up on blocks to break it inand see what happens.
The last time I ran anything full throttle on the layout I was probably 12 years old. If your engine does OK except right at full throttle, I’d forget about it.
You could also check to see that all the bearings and gears are lubricated. If you can, run the loco with no shell (or on stationary locomotive rollers) and see if there are any sticky areas. It is probably a wire rubbing somewhere, but lube never hurts. Don’t forget the bearings on the motor driveshaft.
Len S
Only doing it in one direction makes me suspect worm gear lash is too loose. You adjust this by removing the worm gear from the top of the gearbox, and inserting shim washers in one end so that the worm gear doesn’t move back-and-forth in line with the driveshaft. Put in just enough washers that there is no slop.
I will give it a try. Thanks
To try to determine if it’s the drive train (e.g. excessive gear lash on worm) try pushing the loco along while it’s running and making the noise. Give it just enough force to unload the drivetrain. If the sound disappears, you can really concentrate on the drive train and not something hitting the motor and drive shafts. Also, check the axle gears for any damage.
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