Yes I believe the three shaft boxes work best for a modern tank. I have the 3 shaft set with bearings on all shafts in my Leo and it runs greats. It is the only gearbox that will actually coast and roll downhill. I am setting up an Abrams soon with bearinged up three shaft boxes and a BARC4.
The four shaft boxes will work best in WWII armor. So if you are listening ERIK those four shaft boxes would be best packaged along with your Tigers
Oh I'm listening and yes they will be packaged with the mid version Tiger 1 coming soon
The Jagdtiger will also come with the new 4 shaft steel gearboxes too
The EU versions will have zinc, so just a warning