This document provides assembly instructions for a swing motor used in construction equipment. It describes cleaning and heating parts, inserting springs and other components into the cylinder block and rear cover subassemblies, and assembling the full motor. Tests including an air pressure test and oil leakage check are recommended to check for proper assembly. The motor assembly includes over 30 parts that must be correctly installed and torqued according to specifications.

1. K1016585E Shop Manual
Copyright 2006 DOOSAN
DOOSAN reserves the right to improve our products in a continuing process to provide the best possible
product to the market place. These improvements can be implemented at any time with no obligation to
change materials on previously sold products. It is recommended that consumers periodically contact their
distributors for recent documentation on purchased equipment.
This documentation may include attachments and optional equipment that is not available in your
machine's package. Please call your distributor for additional items that you may require.
Illustrations used throughout this manual are used only as a representation of the actual piece of
equipment, and may vary from the actual item.
Shop Manual
K1016585E
Serial Number 5001 and Up
DX255LC

2. Table of Contents
Page I
1Table of Contents
Safety
Track Excavator Safety......................................................................... SP000014
Specifications
Specification for DX255LC.................................................................... SP001009
General Maintenance
General Maintenance Procedures........................................................ SP000016
Standard Torques................................................................................. SP000813
Upper Structure
Cabin .................................................................................................... SP000943
Counterweight....................................................................................... SP000940
Fuel Tank.............................................................................................. SP001012
Fuel Transfer Pump.............................................................................. SP000021
Swing Bearing....................................................................................... SP001068
Swing Reduction Gear.......................................................................... SP001015
Lower Structure and Chassis
Track Assembly .................................................................................... SP001016
Engine and Drive Train
Drive Coupling (Main Pump)................................................................. SP001069
Hydraulics
Hydraulic System Troubleshooting, Testing and Adjustment ............... SP001017
Accumulator.......................................................................................... SP000028
Center Joint (Swivel)............................................................................. SP000029
Cylinders............................................................................................... SP000030

3. Table of Contents
Page II
Swing Motor.......................................................................................... SP001020
Travel Motor.......................................................................................... SP001021
Gear Pump ........................................................................................... SP000931
Main Control Valve ............................................................................... SP000034
Axial Piston Pump................................................................................. SP001022
PTO Server........................................................................................... SP000933
Remote Control Valve (Work Lever / Joystick)..................................... SP000069
Travel Control Valve (with Damper)...................................................... SP000070
Solenoid Valve Assembly ..................................................................... SP000445
Breaker EPPR Valve (Opt) ................................................................... SP000192
Hydraulic Schematic (DX255LC).......................................................... SP001023
Electrical System
Electrical System .................................................................................. SP001025
Electrical Schematic (DX180LC/DX225LC/225NLC/255LC)................ SP000936
Attachments
Boom and Arm...................................................................................... SP001026
Bucket................................................................................................... SP000939

4. SP001020Swing Motor
Page 24
REASSEMBLY
General Cautions
1. Wash and clean each part. Then dry them with
compressed air. The friction plate, however, should not be
washed with treated oil.
2. Each connecting parts should be tightened according to its
assigned torque.
3. Only use a plastic soft-faced hammer.
Assembly
1. Put roll bearing (3) and bushing (39) on a heater and apply
heat to their inner race (inlet temperature: 290°C for 2
minutes).
!'
!
FG001328
Bushing X 1ea
(SUJ)
Roll Bearing X 1ea
(NUP2209)
Figure 40
FG000715
Figure 41

5. SP001020
Page 25
Swing Motor
2. Assemble heated roll bearing (3) and bushing (39). Use
retaining ring pliers to assemble install retaining ring (7).
3. Put body (1) on assembly jig and secure it so it cannot
move.
4. Assemble oil seal (2) in body (1) using bar hammer.
FG000716
Figure 42
FG000717
Figure 43
FG000718
Figure 44
FG000719
Figure 45

6. SP001020Swing Motor
Page 26
5. Install shaft in body (1) using bar hammer.
6. Secure shaft with retaining ring (4) using retaining ring
pliers.
FG000720
Figure 46
FG000717
Figure 47
FG000721
Figure 48
FG000722
Figure 49

7. SP001020
Page 27
Swing Motor
7. Coat shoe plate (8) with grease, and assemble it into body.
Assembly of Cylinder Block Assembly
Subassembly
8. Insert nine sets of springs (1 thru 9) in cylinder block (9).
FG000723
Figure 50
FG000724
Figure 51
FG000725
Figure 52
FG000726
Figure 53

8. SP001020Swing Motor
Page 28
9. Insert ball guide (1-B-11) in cylinder block (9).
10. Assemble friction plate (14) and plate (15) into cylinder
block (9)
FG000727
Figure 54
FG000728
Figure 55
FG000729
Figure 56
FG000759
Figure 57

9. SP001020
Page 29
Swing Motor
11. Insert piston assembly (1-C-13) in set plate (1-B-12) and
assemble it into cylinder block (9).
NOTE: Coat piston with clean hydraulic oil.
FG000730
Figure 58
FG000731
Figure 59
FG000696
Figure 60
FG000732
Figure 61

10. SP001020Swing Motor
Page 30
12. Assemble cylinder block into body (1).
13. Insert O-ring (38) in body (1).
14. Assemble O-ring (17) into brake piston (16).
FG000733
Figure 62
FG000734
Figure 63
FG000704
Figure 64
FG000687
Figure 65

11. SP001020
Page 31
Swing Motor
15. Insert brake piston assembly in body and secure it using
jig.
16. Insert eighteen springs (18) into brake piston (16).
Assembly of Rear Cover Assembly
Subassembly
1. Insert pins (6 and 21) in rear cover (19) with bar hammer
and assemble needle bearing (20) using jig.
FG000735
Figure 66
FG000736
Figure 67
FG000737
Figure 68
FG000738
Figure 69

12. SP001020Swing Motor
Page 32
2. Assemble O-ring (17) into rear cover (19).
3. Assemble check valve. Install O-ring (27) using jig.
FG000739
Figure 70
FG000740
Figure 71
FG000741
Figure 72
FG000742
Figure 73

13. SP001020
Page 33
Swing Motor
4. Insert poppet (24), spring (25), and plug (26) in rear cover
(19). Tighten plug with L wrench. (Left and right
symmetrically.)
5. Assemble anti-inversion valve. Assemble body, spring
seat, spring, poppet, poppet seat, stopper, and spring.
Then assemble O-ring (31), backup ring (32), and O-ring
(30).
FG000743
Figure 74
FG000708
Figure 75
FG000744
Figure 76
FG000745
Figure 77

14. SP001020Swing Motor
Page 34
6. Assemble anti-inversion valve set. Assemble anti-inversion
valve set and plug assembly (29) into rear cover (19) and
tighten them with L wrench.
7. Assemble plug assembly (36) into rear cover (19) with L
wrench.
FG000711
Figure 78
FG000710
Figure 79
FG000746
Figure 80
FG000747
Figure 81

15. SP001020
Page 35
Swing Motor
8. Assemble two relief valve assemblies into rear cover (19)
with torque wrench. (Left and right symmetrically.)
9. Coat valve plate (1-A-22) with grease and attach it to rear
cover (19).
FG000748
Figure 82
FG000706
Figure 83
FG000749
Figure 84
FG000701
Figure 85

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17. SP001020Swing Motor
Page 36
10. Position rear cover assembly on body (1) and tighten hex
socket head bolt (23).
11. Install time delay valve assembly onto rear cover (19) with
hex socket head bolts (35).
FG000750
Figure 86
FG000751
Figure 87
FG000752
Figure 88
FG000682
Figure 89

18. SP001020
Page 37
Swing Motor
Air Pressure Test
Apply air pressure into assembled motor, dip it in treated oil for
one minute and check any leakage from it.
Oil Leakage Check
Wash motor with Color Check No.1, spray No.3, and check for
any oil leakage.
FG000753
Figure 90
FG000754
Figure 91
FG000755
Figure 92

19. SP001020Swing Motor
Page 38
FG000756
Figure 93
FG000757
Figure 94