Simplicity 1691766, Service & Repair Manual

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7 - 21
7 Transmission Repair
7B Sauer-Sundstrand BDU-21L-207
Bypass Valve
1. Remove the bypass valve plug with a 9/16” hex
wrench. Remove the plug and valve spool.
2. Remove the valve spring from the transmission cen-
ter section.
3. Inspect the valve and mating bore in the center sec-
tion for damage or foreign material. The spool must
move freely in its bore. Replace the valve spool O-
ring.
Retain the spring to the spool with petroleum jelly.
Reinstall the valve spool (with spring) and plug (with O
ring) into the center section. Torque the plug to 8 to 20
ft.lbs. (11 to 27 Nm).
4. Depress the bypass valve several times to insure that
the valve operates smoothly and fully closes.
Figure B-11. Bypass Valve Removal
Charge Pump
DISASSEMBLY
Note: Repairing the charge pump will require the hydro
pump to be removed from the transaxle assembly. See
Section 7A for instructions on separating the hydro pump
from the transaxle.
Important: The correct charge pump orientation is deter-
mined by the rotation of the pump shaft (clockwise or
counter-clockwise). Before removing the charge pump,
make note of, or mark its position to simplify the
reassembly process.
1. Using a 5 or 6 mm internal hex wrench, remove the
two (2) screws holding the charge pump cover to the
center section or end cap.
2. Remove the charge pump cover and O-ring.
3. Remove the charge pump gerotor assembly
4. Remove the charge pump drive pin.
5. Remove the charge relief valve spring and ball.
6. Inspect the gerotor assembly, charge pump cover,
and center section or end cap for abnormal wear,
damage or foreign material. Inspect the charge relief
valve ball and spring. Inspect the charge relief valve
seat in the center section or end cap for damage or
foreign material.
Figure B-12. Charge Pump Cover Orientation
Figure B-13. Charge Pump Components