# USA Train SD 70 Mac



## Large Scale Mark (Apr 11, 2013)

Anybody ever replace the Motor Trucks on this train? Are they hard to replace?


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## josephunh (Mar 27, 2013)

I haven't replaced mine but I have been inside the engine enough times. The wires can pull right off the trucks which is easy enough the harder part is getting inside the take the trucks off. you need to remove the tank underneath to get to some of the screws and the trucks are hiding a few as well. Also there are two very tiny screws on the body edge near the Cab that need to be removed as well.


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## Large Scale Mark (Apr 11, 2013)

Ok Thanks for the help.


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## SD90WLMT (Feb 16, 2010)

The above method of removing the internal bolster screw allows removal of the entire side frame and motor block assembly. 
However, if one is only interested in getting to the motor block itself, one does not need to take out all the cab and hood screws. 

Look from the loco bottom - on the inside of the truck frames. There are 8 nice sized round head phillips screws. Remove 4 on one side only. Carefully remove the wires and label their position also. The motor now can be easily moved sideways to remove it from the still in place side frame. 

You can play with or work on the motor block now! 

BTW......what are you chasing after? Anything wrong inside? 

Dirk


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## Large Scale Mark (Apr 11, 2013)

I have ordered new Truck assembly and I am going to replace it due to having some stripped gears.


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## SD90WLMT (Feb 16, 2010)

Just replace the bad parts... 

How much have you run your loco? 

Dirk


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## Large Scale Mark (Apr 11, 2013)

I ordered the hole assembly thinking it would be easier to change out the truck assembly than to try and get everything to align up just right. I have had this train for over 3 years and ran it about 5 hours a week.


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## SD90WLMT (Feb 16, 2010)

How many cars do you pull with it ? 

Dirk


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## Large Scale Mark (Apr 11, 2013)

I pull about 9 USA Trains and one MTH Dummy Engine


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## SD90WLMT (Feb 16, 2010)

Let's see if I got this all than... 

Short trains = a light load... 

You do not take them apart, hence I conclude they have never had extra grease added...? 

Steady running for 3 years... 

Just leaves me to ask what your grades may be? 

Just getting a "picture" of your experiences with a SD70... 

Dirk


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## Large Scale Mark (Apr 11, 2013)

No grade, I have had this train seviced about a year ago at a train shop. I took it back to the train Shop and they told me I had some stripped gears but they would not work on it unless I could get the gears, I told them I can get the gears, I just figured if I had to order the gears I might as well fix it.


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## honeybooboo (Jan 10, 2014)

Pretty simple to replace trucks, I always go with that option verses just the gears cause I can get the trucks for a reasonable price.

SD 70's are a nice unit and run well and reliably. Change out is simple.

Boo


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## Large Scale Mark (Apr 11, 2013)

Yes I figured it would be easier to change out the whole gear housing than just a few gears, then I will have some extras


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## Randy Stone (Jan 2, 2008)

You need to make sure the new gear boxes have grease in them. Some have found very little grease in the gearbox and this could be why your present gear boxes failed.


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## Large Scale Mark (Apr 11, 2013)

Ok I replaced the trucks and the train still won't move. I get lights and sound will not go forward, if I put the transformer in reverse the power shuts off. Now what could be wrong?


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## Large Scale Mark (Apr 11, 2013)

Ok I replaced the trucks and the train still won't move. I get lights and sound will not go forward, if I put the transformer in reverse the power shuts off. Now what could be wrong?


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## Dan Pierce (Jan 2, 2008)

Possible wiring error? 
If you know how to use a meter, then ohm out the trucks to make sure the track power connections are correct. 
On USA and LGB motor blocks the outer wires are for the motor and inner wires are for the track power. 
When inside the engine, the 2 wire connector is motor, the 4 wires in a 2 wire connector are track power from the motor block. They run extra wires for the pick up shoes.


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## Large Scale Mark (Apr 11, 2013)

I will give that a try, but I think this is the problem I had before I replaced the trucks I was hopping this would have fixed it


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