SkyTrak 3606 Service Manual - Manual (Page 206)

Section 9
9-12
9.7 HYDRAULIC SYSTEM PUMP
The main gear pump (1, Fig. 9–6) is attached to the top
of the transmission and driven via the pump main shaft
via meshing with an internal transmission gear.
The pump draws fluid through a 1-1/2" inside diameter
hose via negative displacement, commonly but incor-
rectly referred to as vacuum or suction.
Fluid is forced from the pump through a 3/4" inside diam-
eter hose to the unloader valve. Hydraulic system pres-
sure begins at the main pump. Various factors are
involved in creating the relatively high pressure used in
the hydraulic system. Main pump rpm, controlled via a
transmission idler gear (and dependent on engine rpm),
in addition to the internal pump gears and passageways,
as well as the differential between pump inlet (1-1/2" I.D.)
and outlet (3/4" I.D.) openings, all contribute to pressure
supplied to the unloader valve. The unloader valve ulti-
mately regulates maximum system-operating pressure
(3500 psi, or 241,5 bar) for various vehicle functions.
9.7.1 Pump, Unloader Valve and Cooling
Circuit
The pump, unloader valve and cooling circuit are shown
for reference purposes in Fig. 9–6.
Oil cooler replacement instructions are provided in the
appropriate engine section of this manual.
9.7.2 Pump Failure Analysis
The pump is the “heart” of the hydraulic system, and
whenever there is a problem in the system, the pump
almost always is blamed. Yet, pump failure is seldom due
to failure of pump components. Pump failure usually indi-
cates another problem in the hydraulic system.
According to pump manufacturer statistics, ninety to
ninety-five percent of pump failures are due to one or
more of the following causes:
• Aeration
• Cavitation
• Contamination
• Excessive heat
• Over-pressurization
• Improper fluid
In the event of pump failure, investigate further to deter-
mine the cause of the problem.
Legend for Pump, Unloader Valve and Cooling Circuit
1. Main Gear Pump
2. Unloader Valve
3. Main Gear Pump Gasket
4. T-Bolt Band Clamp
5. Hose, 1-1/2" I.D. x 19"
6. Hose, 3/4" I.D. x 39"
7. Hose, 3/4" I.D. x 36"
8. Hose, 3/4" I.D. x 81-1/2"
9. Hose, 3/8" I.D. x 89-1/2"
10. Flange Half, 1-1/2"
11. Flange Half, 3/4"
12. Flange Half, 1"
13. O-Ring, 3/4" SF
14. O-Ring, 1" SF
15. O-Ring, 1-1/2" SF
16. Connector, SAE 12-16 - Str. Thd.
ORB x O-Ring Face Seal
17. Plain Washer, 5/16"
18. Plain Washer, 1/2"
19. Lockwasher, 5/16"
20. Lockwasher, 3/8"
21. Lockwasher, 1/2"
22. Hex-head Capscrew, 3/8-16 x 1-1/4"
23. Hex-head Capscrew, 1/2-13 x 1-1/2"
24. Hex-head Capscrew, 5/16-18 x 3-1/4"
25. Dust Plug
26. Diagnostic Nipple
27. Branch Tee, SAE 6 - Str. Thd. ORB x
O-Ring Face Seal
28. Relief Valve Assembly - Preset at
3500 psi (241 bar)
29. Tee, Swivel Run, SAE 12 - o-ring face
seal
30. Diagnostic Nipple
31. Branch Tee, SAE 8 - Str. Thd. ORB x
O-Ring Face Seal
32. Hose, 1/2" I.D. x 28.3" Long
33. Connector, SAE 8 - Str. Thd. ORB x
O-Ring Face Seal
34. Connector, SAE 6 - Str. Thd. ORB x
O-Ring Face Seal
35. Hose, 3/4" I.D. x 28"
36. 90°, SAE 12 - Str. Thd. ORB x O-Ring
Face Seal
37. Male Flat-face Tube Connector, w/
Inlet Check 8ORB-8FF
38. Hose
39. Washer, SAE 5/16"
40. Tie Wrap
Model 3606 • Origin 10/99