I just cleaned and lubricated a Norfolk & Western 746 with a 681 motor. It runs fine on the test bench with rollers but starts and stops intermittently when I put it on the track. The E unit works fine on the test bench and there is no apparent blinding when I roll the wheels manually so I am puzzled and looking for help.
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You may have already done this but: I usually clean wheels, rollers and track. Next, I would clean commutator, brush wells and new brushes/springs. While in there I service/clean e-unit, as well as clean out old grease from gears. Check for cracked/shorted wires. Last you may need new roller springs and or new roller assy. All just very basic service procedures. You can find all you need to know on you tube.
Chris
lock out the E unit and try it in one direction...see if it runs..if it does your problem is likely the E unit...
The axle bushings on the powered axle are probably worn, shifting the worm wheel off center from the worm and the driver into the chassis in forward.
If it runs fine in reverse, this is the likely issue.
The right rear axle bushing is always the one that wears out first(from forward operation), pushing the axle left, the right rear wheel into the frame, and the worm wheel off center.
Of course, the factory fix is to replace the bushing, which requires pulling the 4 rear wheels(two flanged & 2 blind), pressing out the axle from the worm wheel(gear) and the frame, pressing out and replacing the worn bushing(s), and then pressing the axle back in to the chassis and worm wheel, and quartering & pressing the 4 wheels back on.
For an easy fix that will last a long time, use one(or two or as needed) 671M-22 clips/retaining rings and snap them on to the drive axle to the left of the worm wheel. You want to have between half to the full width of a 671M-22 clip of end play in the axle for best performance. Keep the entire gearbox & axle lubed well with a synthetic HP grease(Lucas Red 'N' Tacky #2, eg.).
If you can source some clips with the same inner diameter as the 671M-22, but larger outer diameter, that would be beneficial. The last good tip I heard was to use an appropriate number of plastic bread closure clips(cut to be round) instead of the 671M-22. Very little friction with that method and they too slip right over the axle and stay on.
It is also very important on these to make sure the side rods are not excessively worn and they are oiled with a good synthetic. They transmit power from the geared axle to the other three.
Rob
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