YOKE 5J6156 - Caterpillar

Illustration 1 g01640551
(1) TH31DB (6 Speed) (2) TH35DB (8 Speed)The rear of the transmission has an output transfer gear group, or a drop box, which serves two purposes.
Vertically lowers the propulsive driveline axis.
Couple the two drivelines and uncouple the two drivelines from the engine and transmission power module.During the driving mode, the lower driveline is coupled to the engine and the transmission. The draw works are disengaged. During the well service mode, the draw works driveline is coupled to the engine and transmission. The propulsion driveline is disengaged.Dropbox Operation
The dropbox maintains the same output speeds (constant 1:1 ratio) as the transmission output while providing for the ability to transfer the power flow between multiple output yokes for both stationary use by a work tool and vehicle propulsion. The external features of the dropbox are the same for both the TH31 and TH35 models.The engagement of each disconnect is automatically controlled by the electronic control module (ECM). At no time can the top and bottom disconnect be engaged at the same time. The optional bottom front disconnect can only be engaged while the bottom rear disconnect is engaged. The engagement of any disconnect can only occur when the transmission is in NEUTRAL position, and the engine is at the LOW IDLE, and the machine is stopped.The addition of the dropbox system will increase the oil fill volume to approximately 50 L (13 US gal. ) A larger drop in oil level 12 to 15 L (3.2 to 4 US gal) can be expected in the initial startup. This drop is expected because of the additional lines to fill with oil.