D6D TRACTOR POWER TRAIN – Power Shift Transmission Testing And Adjusting

Power Shift Transmission Schematic

Hydraulic Controls (First Speed Reverse) 1. Torque converter. 2. Body of relief valve for converter outlet. 3. Relief valve for converter outlet. 4. Temperature bypass valve. 5. Water cooled oil cooler. 6. Lubrication line to front of transmission. 7. Air cooled oil cooler. 8. Lubrication relief valve. 9. Lubrication line to rear of transmission. 10. Scavenge oil pump. 11. Oil reservoir for torque converter. 12. Hydraulic controls for steering clutches and brakes. 13. Load piston. 14. Body of pressure control valve. 15. Check valve. 16. Flow control orifice. 17. Relief valve for converter inlet. 18. Body of sequence relief valve. 19. Modulating valve. 20. Pressure differential and safety valve. 21. Pressure relief valve. 22. Oil filter. 23. Bleed line for oil pump. 24. Body of selector valve. 25. Spool for direction selection. 26. Oil reservoir. 27. Magnetic screen. 28. Transmission oil pump. 29. Spool for speed selection. A. Pressure tap for converter outlet. B. Pressure tap for lubrication. C. Pressure tap for converter inlet. D. Pressure tap for sequence relief valve. E. Pressure tap for speed clutches. F. Pressure tap for direction clutches. G. Pressure tap for transmission oil pump.

Location Of The Pressure Taps

A. Torque converter outlet.

C. Torque converter inlet. D. Sequence relief valve.

G. Transmission oil pump.

B. Lubrication. E. Speed clutch. F. Direction clutch.

H. Left steering clutch. I. Right steering clutch. J. Left brake booster. K. Right brake booster.

8P7791 Pressure Control Valve 13. Load piston. 19. Modulating valve. 20. Pressure differential and safety valve. 32. Spacers.

9P1533 Sequence Relief Valve 17. Relief valve for converter inlet. 21. Pressure relief valve. 30. Spacers. 33. Spacers.

2P3675 Relief Valve 3. Relief valve for converter outlet. 31. Spacers.

------ WARNING! ------

When testing must be done in a closed area, activate the brakes and use blocks to prevent the machine from moving during the tests. Let only approved personnel on the machine. Keep other personnel off the machine and


NOTE: All tests and adjustments must be made with the oil in the hydraulic control system at normal operating temperature. Be sure the linkage adjustments are correct before making any tests.


Do not operate the machine with the universal joint removed. The force of hydraulic pressure on the output shaft will cause the shaft to move out of the torque divider. The result is a rapid loss of hydraulic oil.

Selector Valve And Control Linkage Adjustments

------ WARNING! ------

Do not make any adjustments to selector valve or control linkage with engine running.


Adjustment Of Selector Valve Spools

NOTE: Before adjustments are made, make sure nuts (4), (8), and (13) are tightened to a torque of 25 ± 3 lb. ft. (35 ± 4 N·m).

1. Disconnect the control linkage levers from vertical shaft (3) and horizontal shaft (5).

Linkage Adjustment (Inside) 1. Direction cam detent. 2. Direction cam. 3. Vertical shaft. 4. Nut. 5. Horizontal shaft. 6. Detent. 7. Spool for direction selection. 8. Nut. 9. Speed cam. 10. Body of pressure control valve. 11. Spool for speed selection. 12. Body of selector valve. 13. Nut. A. and B. Machined faces of valve body (12).

2. Put detent (1) in the REVERSE groove of direction cam (2), as shown.

Detent In The Reverse Position 1. Detent. 2. Direction cam. 3. Vertical shaft. 7. Spool for direction selection.

3. Loosen the nut on spool (7). Make an adjustment to the length of spool (7) so that the end of the spool is even (flush) with face (A) of selector valve body (12). Tighten the nut on the spool.

4. Put detent (6) in the NEUTRAL groove of speed cam (9), as shown.

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