Service Manual

HYDROSTATIC DRIVE SYSTEM
6-3Fixed Deck Mid-Size Service Manual
6
Fig 712 PICT-6869a
20. Snug fi t the 4 lug nuts on the wheel hub studs (Fig.
712).
Fig 711 PICT-6866
18. Retest the pump after repairs. Re-connect the
hydraulic hoses to the wheel motor fi ttings. Torque
the hose fi ttings to 85-95 ft-lbs. (115-128 Nm).
19. Slide the wheel and tire assembly onto the hub (Fig.
711).
13. Run the machine for 2 minutes in forward (no load)
to purge air from the system.
Note: For accurate test readings, oil must be at
normal operating temperature.
14. Run the machine at full throttle (no load). Verify the
RPM with a tachometer: 3200 + 150 RPM. Do not
exceed 3600 RPM.
15. With the drive control fully forward, slowly tighten the
restriction valve until the gauge indicates 300 PSI
(21 bar).
16. Record the fl ow reading from the bi-directional fl ow
meter. Make a second fl ow reading at 1100 PSI
and record that reading. Subtract the fi rst reading
from the second reading and determine if it is an
acceptable GPM.
Example:
1st Reading: 300 psi (21 bar) reading 7 gpm (26 l/m).
2nd Reading: 1100 psi (76 bar) reading 3 gpm (11 l/m).
7 gpm (1st reading)
- 3 gpm (2nd reading)
4 gpm (the difference)
The acceptable maximum “fl ow droop” or difference is
1.5 gpm (5.6 l/m).
If the difference exceeds these values, the hydrostatic
pump droop is not acceptable.
If the values have been met, the issue would be in the
wheel motor. Refer to “Wheel Motor Replacement” on
page 6-24.
17. Disconnect the fl ow tester and reconnect the
hydraulic lines when test is completed.
Note: Before reconnecting the hydraulic lines,
install new o-rings in the fi ttings.