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 I installed a DigiTracks  DH 465 decoder in this American models GP 35. But it runs very jerky at slow to medium speeds.  Is it the fault of the decoder or is it not appropriate for American models locos.  Anyone else has had and/or solved this problem?  Adding a load to the motor like a couple of cars or a hefty dummy will smooth out the ride.  Check out this vid I made


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Well I oiled everything just to eliminate friction as the culprit.  I think Rusty is right.  I blame the coiled drivers,  it’s as if they are loading up and releasing that energy several times per second.   

I suppose AM had a reason for their design choice.  I just have to accept that this loco will never look good running solo 

Last edited by Martin H

I have a fleet of AM engines converted to TMCC, They are run using Legacy and powered with ZW-L's I have at least one of every diesel AM made EXCEPT the GP35. When operated at the speed shown in your video mine all run smoothly. The difference could be all the ERR boards have either Cruise or Cruise Lite included. I thought the DCC decoders also had a cruise control ability.

If your AM GP35 has the coiled spring Universal joints, that is likely the problem causing the herky-jerky motion. I have a pair of Chessie GP35’s that aren’t that jerky, but I always run them double headed, which tends to smooth them out somewhat. My smoothest operating loco is my AM FP7 that originally came from AM with a Sagami can Motor and what looked like Athearn HO universals. I replaced those universals with a set of universals from Hobbytown, and the drive became so much smoother that I now plan to switch out all of my AM locos to use Hobbytown universals. They are still out there, Google Hobbytown of Boston and give Nick a call.

The spring universals are jerky at low speed because the spring tends to wind up and then suddenly let’s go, then repeats the process, causing the loco to lurch. Adding flywheels and/or double heading will help, but the springs will always be somewhat jerky.

Bill in FtL

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