Hydraulic Drive Flow Test; Replacing The Hydraulic Pump - Gravely Promaster 260Z Service Manual

HYDRAULIC DRIVE FLOW TEST

Use this procedure for trouble shooting the drive
system if the unit becomes sluggish or loss of drive
becomes apparent. This test is to be performed one
side at a time.
1. Block and jack the unit up so that both drive wheels
are off the ground.
2. Place hood into the full service position.
3. Verify that the bypass valves are closed and there
is no binding in the steering control linkage. If
binding occurs, you will need to correct that
problem before proceeding to the next steps.
4. Make sure hydraulic fluid level is correct.
5. Clean hydraulic hoses at the wheel motor.
6. Disconnect the hydraulic hoses at the wheel motor,
note the proper orientation of hoses.
7. Install a bi-directional flow gauge.
8. Have someone depress center of seat to activate
seat switch.
9. Start the engine and run at about 3/4 throttle or
faster. Release parking brake.
10.Stroke the appropriate control lever full stroke
forward and hold.
11.Set the hydraulic system pressure to 200-400 PSI
by using the restriction valve. Note the GPM
(gallon per minute) flow on the meter. While
keeping the pump in full stroke, increase the
hydraulic system pressure to 1000-1200 PSI by
using the restriction valve. Note the GPM flow on
the meter. Do not keep hydraulic system under
pressure for an extended period of time to prevent
damaging the hydraulic system by inducing too
much heat to the system.
12.Open the restriction valve and move the control
lever back to neutral. Idle unit down for a few
seconds and shut off engine.
13.The acceptable flow drop would be less than 1
GPM difference between the low and high pressure
settings. If flow drop is greater than 1 GPM, the
hydro-pump will need to be repaired or replaced. If
the flow drop is less than 1 GPM you will need to
replace the wheel motor.

REPLACING THE HYDRAULIC PUMP

The two hydraulic pumps are located inside the chassis
in front of the engine. The pumps are maintenance free
and should be replaced in the event of a failure. See
Figure 26.
2
To Replace a Hydraulic Pump
1. Lift cover to full service position.
2. Remove the cross channel.
3. Clean hoses and fittings and mark for location.
4. Disconnect hoses from pump.
CAUTION: Some fluid will leak out. Clean up
any spills.
5. Remove belt from pulley.
6. Remove bolt and washers from end of shaft.
7. Loosen pulley lock bolt and slide pulley from shaft.
Remove and inspect square key. Replace key if
damaged.
8. Remove back bolt on pump and loosen front bolt.
9. Remove pump.
10.Insert the new pump into position with the front bolt
in the mounting flange slot.
11.Insert rear bolt and tighten both bolts.
12.Attach hydraulic hoses to correct ports and tighten.
13.Position square key in shaft keyway and slide
pulley into position.
14.Screw the bolt, washer and lock washer into the
end of the shaft. Tighten securely.
15.Tighten pulley lock bolt.
16.Place belt on pulley.
17.Replace cross channel.
18.Lower the cover and start the engine. Run the
engine for 1 - 2 minutes. After shutting off the
engine, check the hydraulic fluid level. The dipstick
should read between the high and low markings.
31
1
1. Hydrostat BDP
Pump
2. Variable-
Displace Pump
Figure 26