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Upgrade and repair Bachmann SD40-2

Started by Desert Rose, July 14, 2022, 07:25:03 PM

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Desert Rose

We purchased 25 new Bachmann-EMD SD40-2 DC/DCC Union Pacific diesel locomotives and 2 Bachmann-EMD SD40-2 w/DCC & Sound Union Pacific diesel locomotives. The idea was to take eight new SD40-2 out of the box, hook them up to eighty 50' high cubes and run them up and down 2% grades in the pacific northwest layout. Using eight new SD40-2 out of the box worked about as good as a screen door on a submarine. This is a list of defects we found in some of the units new out of the boxes:
1). Plastic shell is warped from being removed from the mold to soon causing the back end to warp up.
2). Back coupler sets 1/8 of an inch too high over rolling stock couplers.
3). Wheels in the rear truck don't move, power train problems.                 
4). Motor sounds like a really loud marble grinder. You need to run it up to step 8 to start moving.
5). You can't add sound, there is no place for a speaker, unless you involve a machine shop.

Corrective action:
1). Plastic body shell is warped, Back coupler sets 1/8 of an inch too high.,38183.msg279429.html#msg279429

2). Wheels in the rear truck don't move.
I disassembled the chassis to see why the wheels in the rear truck do not move, the universal joint and the driveshaft was disconnected and lying at the bottom of the driveshaft tunnel.,38176.msg279393.html#msg279393

3). Motor sounds like a really loud marble grinder.

Removed the body shell and DCC decoder board with no sound.
Installed NCE BACH-DSL Decoders P/N: 05240139 installed with no sound.

Adjusted CV's
CV116 torque kick rate to a value of 2.
CV117 torque kick strength to a value of 12.
CV2 start voltage to a value of ().





4). You can't add sound, there is no place for a speaker.

You can Upgrade your Bachmann DC/DCC SD40-2 Diesels with a Soundtraxx TSU-BH1 Tsunami 2 EDM Drop in Digital Sound Decoder for Bachmann Diesels.,38200.msg279496.html#msg279496


I just had this discussion on the Bachmann FB group. The grinding sound is related to the decoder itself, every Bachmann non sound decoder I have has this problem. People on the FB group were under the assumption there were gear problems on the locomotives in question, but that is not what is making the noise, and trying to correct the problem by lubing the gears will not work. The issue of having to use most of the throttle before the locomotive starts to move sounds more like an adjustment of the CV2 start voltage than anything else.

I have a number of Bachmann GP30s, GP35s, GP30s and FTs with the factory decoder, and outside of the noise and the lack of CV5 and CV6 (MAx and Mid voltage settings) i have had little problems with these locomotives. One other adjustment I make is to DJUST the deceleration rate (CV4?) as I have found that unless this is adjusted these units tend to start and stop while pulling a heavy train down a steep grade. I have not had this problem on level track. Allowing these locomotives to coast a little eliminates this problem.
Jeffery S Ward Sr
Pittsburgh, PA

Desert Rose

Lubing gears and replacing truck generally did not solve the nose problems. We found on the DCC installed engines, replacing the decoder board achieved quiet operation. On the DCC ready engines replacing the decoder board achieved a quiet engine, However the drivetrain had a vibrating rattle in it during operation (same for all four DCC ready engines in our inventory). We changed out the Motor w/ Short Flywheel (HO SD40-2), Model: 6090X-8812A-FS. We were able to achieve a quiet operation, all the decoder boards and Motors where changed on the DCC ready engines and both problems where rectified.

At project end, we replaced a total of:
4 sets of trucks
4 motors
6 universal joints.