Postwar wheelsets are COMPLETELY different than MPC and modern era wheelsets and the design intent is different as well.
As an engineer, you'll probably get a kick out of this.
Our trains are expected to go around some absurdly tight curves. While your postwar and MPC freight cars can negotiate a 27" diameter curve, (13.5" radius), two-rail O scale modelers view 36" RADIUS (72" diameter) as an absolute minimum and even that represents a VERY tight curve for prototype trains.
As you're probably well aware, when you have two wheels mounted on an axle traversing a curve, each wheel rotates at a different speed when traversing the curve, the outer wheel rotates faster and covers more length, just like a differential in a car. This is exacerbated when turns get tighter, making the situation in O-gauge 3-rail pretty tricky in order to prevent skidding and drag.
In the prewar and postwar years, this was tackled by allowing the wheels to rotate independently on the axles. The axles are NOT supposed to rotate. That's why collector roller plates and coupler armature plates are mounted right to the axles - they're NOT supposed to spin anyway. These older truck designs MUST be lubricated to roll freely. These cars WILL NOT roll well without lubrication. Once this is done, the car will roll well for several months (in my experience) without needing to be re-lubricated. The difference it will make will be immense. I can pull six postwar cars with nearly ANY locomotive. Even mid-sized non-magnetraction steam locomotives (such as a 2025) can pull 15 or more LUBRICATED postwar cars. A 2383 will pull dozens.
Now, in the MPC era everything changed. Lionel came up with the "fast angle" wheelset. These are a simpler and arguably better solution. They have an ANGLED tread surface, and the wheels are pressed onto the axle. The axle now rotates, has pointed ends, and it rotates in in a slick pointed bearing in the sideframe. This minimizes contact area and gives VERY low rolling resistance. The angled wheel treads allow the wheelsets to automatically adjust to curves. When going around a curve, the "outside" wheel flange is naturally pressed against the rail through centrifugal force. This causes the large end of the wheel tread's taper to ride on the rail while the opposite occurs on the "inside" of the curve - the small end of the taper rides the rail. This creates a natural differential and allows both wheels to roll freely without skidding.
Officially these modern trucks require no lubrication, but I still often add a tiny dab of grease to the needlepoint axle ends, if anything, just to prevent wear.
It's true that the older design prewar and postwar wheels will never roll as freely as the modern equipment, but the difference is fairly negligible IF the older cars are kept properly lubricated.
Use a needlepoint oiler and add drop of lightweight oil each side of each wheel, then spin the wheels back and forth by hand to encourage it to flow between the wheel and axle. Do the rollers as well (modern cars still require roller lubrication).
