TRANSMISSION/STEERING VALVE TRANSMISSION
7C - 131
1. Valve Body 18. ½NC Hex Nut 35. Detent Ball
2. Expander Plug 19. Dowel Pin 36. Range Detent Spring
3. Port Plug 20. Dowel Pin 37. Detent Guide
4. Steering Spool 21. Range Cam 38. Detent Guide Plug
5. Pickup Spacer 22. Bottom Cover 39. O-ring
6. Inner Spring 23. Cover Plug 40. Switch Arm
7. Outer Spring 24. Orifice Plug 41. Ceramic Ring Magnet
8. Directional Spool 25. Dowel Pin 42. Brass Screw
9. Spring Retainer Washer 26. Motion Lever 43. Locking Bolt
10. Forward Reverse Spring 27. Bearing Housing 44. Wiper Seal
11. Retainer Nut 28. Cam Ring 45. Wiper Seal
12. Spool Rocker End 29. Ball Bearing 46. Wiper Seal
13. dNC Jam Nut 30. Retaining Ring 47. O-ring
14. Range Spool 31. Universal Joint 48. O-ring
15. Thrust Bearing 32. Joint Boot 49. O-ring
16. Thrust Washer 33. Tie Strap
17. Dowel Pin 34. Dowel Pin
DESCRIPTION
The transmission/steering valve is a manually controlled direction, range and steering control valve. The valve is used
to direct main oil pressure to the transmission range selector valve for transmission control and to the steering drive
clutches for steering control. A detent mechanism holds the control lever in the desired transmission selection.
THEORY OF OPERATION
Main pressure from the main regulator valve enters the motion control valve at the “P” port and is distributed along and
through the range spool and around the range spool to the direction and steering spools. When the control lever is in
the centered “neutral” position, oil is active at the selected range port and steering ports but is blocked at the direction
spools.
When the control lever is moved forward, the cam plate depresses the forward direction spool directing oil to the “F”
port at the bottom of the valve. The “F” pressure is also directed internally to the base of the Reverse spool which
pushes the reverse spool up to the cam plate, this action creates a hydraulic detent holding the lever forward. When
pulling the control lever to neutral or reverse, the cam plate pushes down on the reverse spool which displaces the
hydraulic detent oil. At the same time the forward spool follows the cam plate up and mid way through its stoke the
forward pressure is cut off as well as the reverse hydraulic detent, allowing the valve to go into neutral. If the lever is
pulled all the way to reverse the same sequence of events happens for the reverse hydraulic detent.
A transmission range gear is selected by rotating the control lever. If rotated counterclockwise to the left most position
1st gear is selected, pressure is sent to the 1st gear pilot port of the range selector valve. Rotating the control lever
clockwise one detent position will select 2nd gear, pressure is sent to the 2nd gear pilot port of the range selector.
Rotating one more position clockwise will select 3d gear, no pressure is sent in 3rd gear since the range selector is
normally in 3rd gear without pressure. The range detent positions are provided by a steel ball, spring and 4 steel pins
located in the cover of the valve.
Steering is accomplished by moving the control lever to the left or right. With the control lever in the upright position both
tracks are driven equally and the tractor travels straight ahead. Pulling the control lever to the right will begin a right hand
turn. The initial movement of the lever drops the right steering clutch pressure causing the right steering clutch to be
in a neutral condition. The neutral condition is indicated by a “feel point” or effort increase in the control lever movement.
Further movement of the control lever to the right increases pressure in the right brake clutch which if pulled to the end
of the lever stoke will result in a pivot turn. A left hand turn is accomplished by pushing the lever to the left. The same
“feel point” feature and series of events takes place as with the right hand turn.
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