This Lionel 8770 EMD NW2 switcher (blt. 1977) was purchased in Edmonton (AB) in 2000. It ran nicely forward, but did not want to reverse. In reverse mode the motor made all kind of buzzing sounds and hardly moved. The motor clearly looked fully restored and most parts were amazingly clean for a toy train engine of this age. The central axle of the electromotor was found to move 5 mm down in reverse and 5 mm up in forward. In forward mode the brush springs push the axle sufficiently down, but in reverse mode the axle is not corrected by a spring and the transmission between the wormwheel and gear gets frustrated and it blocks. I tried adding several rings to minimise the vertical displacement of the axle and finally that worked. Two thin rings on the bottom (1 mm metal M2 ring with 2 mm plastic ring on top of that) and a larger ring on the commutator (4 mm high, cut from a drill plug) did the trick. The switcher likes to go forward and backward again!
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