D155 Gear box is a three-degree freedom gear box
with 3 forward and 3 backward speed, consisting of 4
planetary gear groups and 5 disc clutches. The first 2
planetary gear groups and related disc clutches are
designed to control the backward and forward. The other 2
planetary groups and 3 disc clutches are used for controlling
1st gear, 2nd gear and 3rd gear. The 1st , 3rd and 4th planetary
groups are single gear transmissions. The 2nd planetary group
is a double gear transmission, designed for backward
There are 2 types of clutch: The 1st , 2nd , 3rd and 4th are used
for fixing the ring gear, also called break clutch or break.
The 5th clutch, called lockup clutch, is used for combining the driving and driven parts,
so that the system can rotate together.
By shifting the control valve, the hydraulic pressure will engage 2 clutches, so a certain rotation speed and rotation direction will be output.
The main product line includes gear box assembly for bulldozers of Komatsu D155, D85, D65 and Caterpillar D6D, D7G.