Converting MTH 3-Rail Trucks to Atlas 3-Rail Trucks

You will encounter a bit of a problem as MTH trucks have the machine threads in the truck bolster, in order to accept the mounting machine screw from inside the carbody. All Atlas trucks are designed to have the mounting screw pass through the truck bolster and screw into the car under frame. Thus, you will probably have to use a screw with a locking nut inside the car, in order to effectively mount the Atlas truck. Then of course there might be the height difference between an MTH truck and an Atlas truck.

Just curious; why do you want to replace the MTH trucks with Atlas trucks?

As a practical matter, while the Atlas trucks now have rotating bearing caps, I don't think you gain that much switching from MTH 3-rail trucks to Atlas 3-rail trucks. Usually this type of discussion is related to 2-rail conversion.

That said, a simple way to mount Atlas trucks to an MTH car is to get a small section of 3/16" wood doweling and mount it into the MTH chassis, then enlarge the hole in the Atlas truck to 3/16" and use the Atlas mounting screw to hold it on the dowel. I've used this trick to fix Atlas cars that had the mounting stud snap.

I appreciate the feedback. I think I figured out how to use the parts that come with the Atlas couplers to work in a fashion similar to what Matt suggests.  Even better, I don't have to do any modifications to the car body.

As for why the Atlas trucks? Besides the rotating bearing caps, the principal reason is to lower the car body a little where it looks more prototypical.  IMHO with many MTH cars (and some Lionel ones as well), the car body rides too high above the rails.  The downsides to the switch is that the cars will not accommodate as tight corners.  However, in my case the sharpest turn on my layout, except for a couple spurs, is O 48.

I just did this, use the little Delrin washers that come with the Atlas trucks. You mount them in the hole where the Mth truck goes, then you can use the Atlas screw from the out side. I did this mounting Weaver trucks to MTH.

While Atlas trucks sit a little lower in many cases, they are also wider in many cases.    for example on the USRA boxcars, the journals are even with the sides and they should be underneath the car.    Just some food for thou ght.

@prrjim posted:

While Atlas trucks sit a little lower in many cases, they are also wider in many cases.    for example on the USRA boxcars, the journals are even with the sides and they should be underneath the car.    Just some food for thou ght.

True for the older trucks. The newer ones addressed that issue and have narrower side frames and shorter axles (the old axles don't fit into the new trucks).