The dimensions for the Lionel axles (new) are 4.05mm for both journals while the spline for the gear comes out at 4.30mm. The bushes bore is 4.15mm, 2mm thick and 7.90mm diameter. So it would seem that the gear was put on the axle in the chassis and the bushes then slipped over the axles and pushed into the chassis. The chassis thickness is not the same for each side, one side is 3.34mm and the other is 3.50mm, not that it makes any difference really.
I have rebuilt a few of mine and use the same bush that I use in the ACG chassis except I take out the bore to 4.10mm while the thickness of the bush is 4.00mm, twice that of the Lionel one. Another interesting fact is the measurement of a Lionel axle after it has been pitted by electrical arcing comes out at 4.10mm
Hop this helps if anyone is interested
