Abstract: Two-way transmission gears in which each power branch includes an intermediate shaft, each shaft being mounted for rotation in a different (separate) gear case portion, and in which the power distribution is effected by means of an axially freely adjustable shaft provided with double helical teeth extending in opposite directions, require for the assembling and disassembling thereof and for adjustment purposes at least one gear which is positioned for displacement and adjustment relative to another gear disposed on the same shaft. In the subject matter of the invention, it is contemplated normally to do without a displaceable and adjustable gear, in that the power-distributing shaft provided with pinions having oppositely extending helical teeth is axially displaced or shifted during the assembly or disassembly. A method for assembling two-way transmission gears is disclosed, also.