Double planetary gears are used in NW and NGWN planetary transmissions.

For a planetary transmission with double planetary gears, in order to make each planetary gear fit into the central gear from the axial direction without interference, the tooth position orientation of the two ring gears of each planetary gear in the same transmission must be the same, that is to say, there must be one tooth in the two ring gears or the symmetrical center line between the teeth (groove) must be in the same plane. This problem has been considered in manufacturing, and the alignment mark has been marked on the tooth for the basis of positioning during assembly.

When the number of teeth of each center meshed with the planetary gear is an integral multiple of the number of planetary gears, only the alignment mark line of each planetary gear and the coupling center lines o Ⅰ, O Ⅱ, O Ⅲ on the bogie are needed for assembly Align and install. At this time, there must be a symmetrical center line and coupling center lines o Ⅰ, O Ⅱ, O Ⅲ between teeth (grooves) on each center wheel Coincide.

When the number of teeth of the central wheel cannot meet the above requirements, the alignment marking lines of each planetary wheel are not in the same phase. During assembly, the alignment mark line of planetary wheel 1 shall be placed on line o I. The alignment mark lines of other planetary gears must be connected with the connecting center lines o Ⅱ and O Ⅲ , corresponding to  2,  3 A certain angle of can be installed into the central wheel. The rotation angle of each planet  2,  3 Depending on the design parameters such as the number of center teeth, the assembly can be carried out according to the marks made by the manufacturer on the corresponding meshing teeth. If there is no engagement mark, trial assembly can be carried out tooth by tooth to determine its position.

Other requirements in the assembly are the same as those of NGW planetary transmission.