Service Manual

Axial Piston Pumps
DDC20/24

www.danfoss.com

Service Manual
DDC20/24 Axial Piston Pumps

Revision history

2 | © Danfoss | December 2023

Table of revisions
Date

ChangedRev

December 2023

Changed document number from 'AX00000135' and 'L1120413' to 'AX152986482107'

0503

August 2019

Added DDC24

0401

August 2017change charge pump housing

0302

March 2015

add implement pump option

CA

March 2014

Danfoss layout

BA

September 2011

First printing

AA

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DDC20/24 Axial Piston Pumps
Contents
Introduction
Overview..............................................................................................................................................................................................4
Warranty.............................................................................................................................................................................................. 4
General instructions........................................................................................................................................................................ 4
Remove the unit.......................................................................................................................................................................... 4
Keep it clean..................................................................................................................................................................................4
Lubricate moving parts.............................................................................................................................................................4
Replace all O-rings and gaskets............................................................................................................................................. 4
Secure the unit............................................................................................................................................................................. 5
Safety Precautions............................................................................................................................................................................5
Unintended machine movement..........................................................................................................................................5
Flammable cleaning solvents................................................................................................................................................. 5
Fluid under pressure.................................................................................................................................................................. 5
Personal safety............................................................................................................................................................................. 5
Gauge port locations and installation
Gauge port locations and sizes- with Aux pad...................................................................................................................... 6
Gauge port locations and sizes- with Gerotor....................................................................................................................... 7
Gauge port locations and sizes- with Implement pump....................................................................................................8
Adjustments
Pump adjustment.............................................................................................................................................................................9
Standard Procedures.......................................................................................................................................................................9
Charge pressure relief valve......................................................................................................................................................... 9High pressure relief valve............................................................................................................................................................10
Loop flushing valve....................................................................................................................................................................... 11
Troubleshooting
Troubleshooting Overview.........................................................................................................................................................12
System operating hot...................................................................................................................................................................12
Transmission operating normally in one direction only..................................................................................................12
System noise or vibration........................................................................................................................................................... 12
System will not operate in either direction.......................................................................................................................... 12
Sluggish system response...........................................................................................................................................................13
Minor repair
Charge pump...................................................................................................................................................................................14
Implement pump...........................................................................................................................................................................16
Shaft and shaft seal....................................................................................................................................................................... 17High pressure relief valve (HPRV)............................................................................................................................................. 21
Charge pressure relief valve (CPRV)........................................................................................................................................ 22
Loop flushing valve....................................................................................................................................................................... 23
Bypass valve..................................................................................................................................................................................... 24
Optional coupling..........................................................................................................................................................................25
Torque charts
Charge pump fastener and torque chart.............................................................................................................................. 26
Implement pump fasteners and torque chart.....................................................................................................................26
Gerotor plugs and torque........................................................................................................................................................... 27
Auxiliary pad plug sizes and torque chart.............................................................................................................................28
Implement pump plug sizes and torque chart................................................................................................................... 29© Danfoss | December 2023

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Service Manual
DDC20/24 Axial Piston Pumps
Introduction
Pump service overview
This manual includes information on maintenance, troubleshooting, and minor repair of DDC20/24
pumps.
Performing minor repairs may require removal from the vehicle/machine. Thoroughly clean the unit
before beginning maintenance or repair activities. Since dirt and contamination are the greatest enemiesof any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially importantwhen changing the system filter and when removing hoses or plumbing.
A worldwide Global Service Partner Network is available for major repairs. Major repairs require theremoval of the unit’s endcap, which voids the warranty unless done by a Global Service Partner. Danfoss
Global Service Partners are trained by the factory and certified on a regular basis. You can locate yournearest Global Service Partner using the distributor locator at www.danfoss.com.
For detailed technical information, refer to the Technical Information manual.
Warranty
Performing maintenance, and minor repairs according to the procedures in this manual will not affectyour warranty. Major repairs requiring the removal of the units endcap voids the warranty unlesscompleted by a Danfoss Global Service Partner.
General instructions
Remove the unit

Prior to performing major repairs, remove the unit from the vehicle/machine. Chock the wheels on thevehicle or lock the mechanism to inhibit movement. Be aware that hydraulic fluid may be under highpressure and/or hot. Inspect the outside of the pump and fittings for damage. Cap hoses and plug ports
after removal to prevent contamination.
Keep it clean

Cleanliness is a primary means of assuring satisfactory pump life, on either new or repaired units. Clean
the outside of the pump thoroughly before disassembly. Take care to avoid contamination of the system
ports. Cleaning parts using a clean solvent wash and air drying is usually adequate.
As with any precision equipment, keep all parts free of foreign materials and chemicals. Protect all
exposed sealing surfaces and open cavities from damage and foreign material. If left unattended, cover
the pump with a protective layer of plastic.
Lubricate moving parts

During assembly, coat all moving parts with clean hydraulic fluid. This assures that these parts arelubricated during start-up.
Replace all O-rings and gaskets

Danfoss recommends you replace all O-rings, seals, and gaskets during repair.Lightly lubricate all O-rings
with clean petroleum jelly prior to assembly. Grease must be soluable in hydraulic fluid.
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DDC20/24 Axial Piston Pumps
Introduction
Secure the unit

For major repair, place the unit in a stable position with the shaft pointing downward. It is necessary tosecure the pump while removing and torquing components and fasteners.
Safety Precautions
Always consider safety precautions before beginning a service procedure. Protect yourself and othersfrom injury. Take the following general precautions whenever servicing a hydraulic system.
Unintended machine movement

W Warning
Unintended movement of the machine or mechanism may cause injury to the technician or bystanders.
To protect against unintended movement, secure the machine or disable/disconnect the mechanism
while servicing.
Flammable cleaning solvents

W Warning
Some cleaning solvents are flammable. To avoid possible fire, do not use cleaning solvents in an area
where a source of ignition may be present.
Fluid under pressure

W Warning
Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious
injury and/or infection. This fluid may also be hot enough to cause burns. Use caution when dealing withhydraulic fluid under pressure. Relieve pressure in the system before removing hoses, fittings, gauges, orcomponents. Never use your hand or any other body part to check for leaks in a pressurized line. Seek
medical attention immediately if you are cut by hydraulic fluid.
Personal safety

W Warning
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.

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DDC20/24 Axial Piston Pumps
Gauge port locations and installation
DDC20/24 gauge port locations and sizes- with Aux pad
The following drawing and table show the gauge port locations and gauge sizes needed.
DDC20/24 with aux pad
M3 Charge gauge / E - Charge inlet
O-ring plug 9/16-18UNF-2B

L1 Case Drain
O-ring Plug 3/4-16UNF-2B

System port A

System port B
L2 Case Drain
O-ring Plug 3/4-16UNF-2B

MA system pressure gauge port
O-ring plug 9/16-18UNF-2B

M3 Charge gauge / E - Charge inlet
O-ring plug 9/16-18UNF-2B

L3 Case Drain
O-ring Plug 3/4-16UNF-2B

MB system pressure gauge port
O-ring plug 9/16-18UNF-2B

Port Information

6 | © Danfoss | December 2023

Port Identifier

Port Size

Wrench Size

L1/L2/L3

3/4-16 UNF

5/16 inch internal hex Case Drain

Pressure Obtained

10 [100]

Gauge Size, bar [psi]MA/MB

9/16-18 UNF

11/16 hex wrench

System Pressure

500 [5000]

M3/E

9/16-18 UNF

1/4 inch internal hex

Charge Pressure

50 [1000]

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DDC20/24 Axial Piston Pumps
Gauge port locations and installation
DDC20/24 gauge port locations and sizes- with Gerotor
The following drawing and table show the gauge port locations and gauge sizes needed.
DDC20/24 with gerotor
L1 Case Drain
O-ring Plug 3/4-16UNF-2B

M3 Charge Pressure Gauge Port
O-ring Plug 7/16-20UNF-2B

MA system pressure gage port
O-ring plug 9/16-18UNF-2B
S -Chargesuction port

MB system pressure gage port
O-ring plug 9/16-18UNF-2B

L3 Case Drain
O-ring Plug 3/4-16UNF-2B

Port Information
Port Identifier© Danfoss | December 2023

Port Size

Wrench Size

Pressure Obtained

Gauge Size, bar [psi]L1/L2/L3

3/4-16 UNF

5/16 inch internal hex

Case Drain

10 [100]

MA/MB

9/16-18 UNF

11/16 hex wrench

System Pressure

500 [5000]

S

7/8-14 UNF

N/A (plastic shipping plug)

Charge Inlet

2 [30] VacuumM3

7/16-20 UNF

3/16 inch internal hex

Charge Pressure

50 [1000]

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DDC20/24 Axial Piston Pumps
Gauge port locations and installation
DDC20/24 gauge port locations and sizes- with implement pump
The following drawing and table show the gauge port locations and gauge sizes needed.
DDC20/24 with implement pump
M3 Charge Gauge/
E Implement Return

A System Port

L1 Case Drain
O-ring Plug 3/4-16UNF-2B

M3 Charge Pressure Gauge PortE Implement Return
O-ring Plug 9/16-18UNF-2B

O-ring plug 9/16-18UNF

B System PortMA system pressure gage port
O-ring plug 9/16-18UNF-2B

L2 Case Drain Port
O-ring plug 3/4-16UNF-2B

D Implement Discharge
O-ring plug 9/16-18UNF-2B

S -Chargesuction port

MB system pressure gage port
O-ring plug 9/16-18UNF-2B

L3 Case Drain
O-ring Plug 3/4-16UNF-2B

Port Information

8 | © Danfoss | December 2023

Port Identifier

Port Size

Wrench Size

L1/L2/L3

3/4-16 UNF

5/16 inch internal hex Case Drain

Pressure Obtained

10 [100]

Gauge Size, bar [psi]MA/MB

9/16-18 UNF

11/16 hex wrench

System Pressure

500 [5000]

S

7/8-14 UNF

N/A (plastic shipping
plug)

Charge Inlet

2 [30] VacuumD

9/16-18 UNF

1/4 inch internal hex

Implement Pressure

100 [2000]

M3/E

9/16-18 UNF

1/4 inch internal hex

Charge Pressure

50 [1000]

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DDC20/24 Axial Piston Pumps
Adjustments
Pump adjustment
This section offers instruction on adjustment of pump components. Read through the entire topic before
beginning a service activity. Refer to Gauge port locations and installation for location of gauge ports andsuggested gauge size.
Standard Procedures

C Caution
Contamination can damage internal components and void the manufacturer’s warranty. Take
precautions to ensure system cleanliness when removing and reinstalling system lines
1. With the prime mover off, thoroughly clean the outside of the pump.
2. If removing the pump from the machine, tag each hydraulic line connected to the pump. If hydrauliclines are disconnected, plug each open port, to ensure that dirt and contamination do not get into
the pump.
3. Ensure the surrounding areas of the machine are clean and free of contaminants such as dirt andgrime.
4. Look at the hydraulic fluid for signs of system contamination, oil discoloration, foam in the oil, sludge,
or small metal particles.
5. If there are signs of contamination in the hydraulic fluid, drain the hydraulic system, replace all filters,
flush the lines and fill the system with the proper hydraulic fluid.
DDC20/24 charge pressure relief valve adjustment
The following procedure explains how to check for proper operation of the charge pressure relief valve.
Charge pressure is the measured pressure minus case drain pressure.
1. Install a 50 bar [1000 psi] pressure gauge at the charge pressure gauge port. Install a 10 bar [100 psi]
gauge at one of the case pressure ports. Operate the system with the pump in neutral (zerodisplacement) when measuring charge pressure.
Pressure listed in model code assumes a charge flow of 15 l/min [4 US gal/min], and are referenced tocase pressure. At higher charge flows, the charge pressure will rise over the rated setting.
2. The table shows the acceptable pump charge pressure range for some nominal charge relief valve
settings (refer to model code located on serial number plate).
3. If measured pressure is not correct, disassemble the valve and look for signs of wear orcontamination. Refer to the Torque charts chapter for wrench sizes and torque settings.
4. If the valve is worn, replace the entire valve assembly.
5. Re-check the charge pressure setting.

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DDC20/24 Axial Piston Pumps
Adjustments
6. When the desired charge pressure setting is achieved, remove the gauges.
Charge pressure relief valve
J320
QJ040

L200
L100

P109626

Charge pressure
Model code

Charge pressure1

07

7 bar ± 1 bar

18

18 bar ± 1.5 bar

1 The shown values are calculated by subtracting the case pressure port gauge reading from the charge pressuregauge reading.

Factory set at 1800 min-1 (rpm) with a reservoir temperature of 50° C [120° F].
DDC20/24 high pressure relief valve (HPRV) adjustment
The HPRV valves are set at the factory. No adjustment is possible.
If you suspect a HPRV valve malfunction, replace valve with identical relief setting and test operation of
pump. Refer to Removal for replacement procedures.
When replacing or opening an HPRV, check for proper pump operation by cycling through its fulloperating range.

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DDC20/24 Axial Piston Pumps
Adjustments
HPRV valve locations

QJ020

J150
P100
P110

N110
N100
J140

QJ020
P109625

DDC20/24 loop flushing valve adjustment
The loop flushing valve is not adjustable.
If the loop flush valve is malfunctioning, disassemble the valve and check for worn, damaged or scoredcomponents. Replace parts if necessary. Refer to Removal for replacement procedures.
Loop flushing valve locations

J230

H150

H200

H100
H200
H150
J220

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Service Manual
DDC20/24 Axial Piston Pumps
Troubleshooting
Troubleshooting Overview
This section serves as a guide for identifying and resolving undesirable system conditions.
Please observe the safety concerns listed in Safety Precautions on page 5 and the precautions related to
relevant equipment when resolving system issues.
DDC20/24 system operating hot
Cause

Problem

Solution

Oil level in reservoir. Insufficient hydraulic fluid will not meet cooling demands ofsystem.

Fill reservoir to proper level.

Heat exchanger.

Heat exchanger not sufficiently cooling the system.

Check air flow and input air temperature for heat exchanger.
Clean, repair or replace heat exchanger.

Charge pressure.

Low charge pressure will overwork system.

Measure charge pressure. Inspect and/or replace charge relief
valve. Inspect charge pump. Repair or replace charge pump.

Charge pump inlet
vacuum.

High inlet vacuum will overwork system. A dirty filter will
Check charge inlet vacuum. If high, inspect inlet filter andincrease the inlet vacuum. Inadequate line size will restrict flow. replace as necessary. Check for adequate line size, length orother restrictions

System relief
pressure settings.

If the system relief valves are worn, contaminated, or valve
settings are too low, the relief valves will be overworked.

Verify settings of high pressure relief valves and replace valves
as necessary.

System pressure.

Frequent or long term operation over system relief setting will
create heat in system

Measure system pressure. If pressure is too high, reduce loads.

DDC20/24 transmission operating normally in one direction only
Cause

Problem

SolutionControl linkage

Control linkage operating improperly

Repair/replace control linkage

High pressure relief
valve

Malfunctioning HPRV can affect one direction while the otherfunctions normally.

Exchange the high pressure relief valves. If the problem
changes direction, replace the valve that does not operatecorrectly. Settings may be different for forward/reverse.

DDC20/24 system noise or vibration
Cause

Problem

Solution

Oil level in reservoir Low oil level leads to cavitation.

Fill reservoir.

Aeration of the oil/ Air in system decreases efficiency of units and controls. Air inpump inlet vacuum system is indicated by excessive noise in pump, foaming in oil,and hot oil.

Find location where air is entering into the system and fix.
Check that inlet line is not restricted and is proper size.

Cold oilIf oil is cold, it may be too viscous for proper function and cause Allow the oil to warm up to its normal operating temperaturecavitation
with engine at idle speed.

Pump inlet vacuum High inlet vacuum causes noise/cavitation.

Check that inlet line is not restricted and is proper size. Checkfilter and bypass valves (if present).

Shaft couplings

A loose shaft coupling will cause excessive noise.

Replace loose shaft coupling.

Shaft alignment

Misaligned shafts creates noise

Align shafts.

Charge/Highpressure relief
valvesUnusual noise may indicate sticking valves. Possible
contamination.

Clean/replace valves and test pump. May be a normal
condition.

DDC20/24 system will not operate in either direction
Cause

Problem

Solution

Oil level in reservoir Low oil level leads to cavitation.

Fill reservoir.

Open bypass valve

Close bypass valve.

If bypass valve is open, the system loop will be depressurized.

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DDC20/24 Axial Piston Pumps
Troubleshooting
Cause

Problem

Solution

Low charge
Low charge pressure insufficient to recharge system looppressure with pumpin neutral

Measure charge pressure with the pump in neutral. If pressure islow, go to Pump charge relief valve

Low charge
Low charge pressure resulting from elevated loop leakage.
pressure with pumpin stroke

Isolate pump from motor by blocking system ports. With pumpin partial stroke and engaged for only a few seconds, checkpump charge pressure. Low charge pressure indicates amalfunctioning pump. Continue to next step. Good chargepressure indicates a malfunctioning motor or other systemcomponent. Check motor charge relief operation (if present).

Pump charge relief
valve.

A pump charge relief valve that is leaky, or contaminated, or set Replace pump charge relief valve as necessary
too low will depressurize the system.

Charge pump inlet
filter.

A clogged filter will under supply system loop.

Inspect filter and replace if necessary.

Charge pump.

A malfunctioning charge pump will provide insufficient charge
flow.

Repair or replace the charge pump.

System pressure

Low system pressure does not provide enough power to moveload

Measure system pressure. Continue to next step.

High pressure relief
valvesDefective high pressure relief valves cause system pressure to
be low

Replace high pressure relief valves.

Control Linkage

Linkage operating improperly

Repair/replace control linkage

DDC20/24 sluggish system response
Cause

ProblemOil level in reservoir Low oil level causes slower system response

Solution
Fill reservoir

High pressure relief
valvesIncorrect system pressures will affect system reaction time. High Replace high pressure relief valvespressure relief valve with orifice may affect system reactiontime.

Low prime mover
speed

Low engine speed will reduce system performance

Adjust engine speed

Air in system

Air in system will produce slower system response

Fill tank to proper level. Cycle system slowly for several minutes
to remove air from system

Pump inlet vacuum Inlet vacuum is too high resulting in reduced system pressure.

Measure charge inlet vacuum. Inspect line for proper sizing.
Replace filter. Confirm proper bypass operation.

Bypass valve

Verify that the bypass valve is closed and that the valve isseating properly. Clean, repair, or replace it as necessary.

Slightly activated bypass valve will cause cross port leakage.

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Service Manual
DDC20/24 Axial Piston Pumps
Minor repair
Charge pump
DDC20/24 charge pump disassembly
Charge pump cover orientation
Clockwise rotation

Counterclockwise rotation

Flat
side

Flat
side

P109624

Please note the orientation of the charge pump during disassembly (clockwise and counterclockwise).
1. Position the pump with the shaft end pointing down.
2. Mark the orientation of the charge pump cover on the endcap for proper reassembly.
3. Remove cap screws (K200). Remove the charge pump cover (K150).
4. Remove and discard O-ring (K100).
5. Remove gerotor (K010). Push out the drive pin (K050).
DDC20/24 charge pump, implement pump and gerotor inspection
Inspect all machined surfaces for wear or damage. If any nicks, scratches or wear are found replace
the cover and/or gerotor.

DDC20/24 charge pump assembly
1. Install drive pin (K050) into the shaft.
2. Lubricate and install the gerotor (K010).
3. Lubricate and install O-ring into cover (K100).
4. Install the housing in its original position (K150).
5. Install screws (K200). Torque screws per table.

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DDC20/24 Axial Piston Pumps
Minor repair
DDC20/24 Remove charge pump

K200

K150
K100

K010

K050

P109623

Charge pump cover mounting bolts© Danfoss | December 2023

Item

Wrench size

TorqueK200

6 mm internal hex

20 N•m [15 lbf•ft]

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Service Manual
DDC20/24 Axial Piston Pumps
Minor repair
Implement pump
DDC20/24 implement pump removal
1. Position the pump with the shaft end pointing down.
2. Remove cap screws (K200/K210). Remove the implement pump housing (K150).
3. Remove and discard O-ring (K100/K110).
4. Remove gerotor (K010). Remove locating pins (K250) from housing.
Remove implement pump
K210
K200

K150

K250

K110

K100

K010

Implement pump cover bolts

16 | © Danfoss | December 2023

Item

Description

Wrench size

TorqueK200

Cap screw

8 mm internal hex

60 N･m [44 lbf･ft]

K210

Cap screw

8 mm internal hex

39 N･m [29 lbf･ft]

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DDC20/24 Axial Piston Pumps
Minor repair
DDC20/24 charge pump, implement pump and gerotor inspection
Inspect all machined surfaces for wear or damage. If any nicks, scratches or wear are found replace
the housing and/or gerotor.

DDC20/24 implement pump assembly
1. Install locating pins (K250) into the endcap.
2. Lubricate and install gerotor (K010).
3. Lubricate and install O-ring (K100/K110) into housing (K150).
4. Install housing (K150).
5. Install screws (K200/K210). Torque screws per table.
Shaft and shaft seal
DDC20/24 shaft seal removal
1. Orient pump with the shaft pointing up.
2. Using a retaining ring pliers, remove retaining ring (F125).
3. Remove the shaft seal (F120) and discard.

C Caution
Do not damage the housing bore, shaft or bearing when removing the shaft and shaft seal.
Carefully drive a small sheet-metal screw into the shaft seal to facilitate removal. Be careful not todamage the bearing below the seal. Attach a slide hammer or appropriate puller to the screw headand pull to remove the seal.

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Service Manual
DDC20/24 Axial Piston Pumps
Minor repair
Remove Seal, Shaft, Bearing

F125

F120

F115

F110

F105

F100

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DDC20/24 Axial Piston Pumps
Minor repair
DDC20/24 shaft removal
1. Using a retaining ring pliers, remove retaining ring (F115).
2. Pull the shaft (F100), with bearing (F105), out of the pump. If necessary, tap lightly on the shaft todislodge it from the internal pump components.

C Caution
Moving the pump with the shaft removed may dislodge the rotating group making reassembly
impossible without removing the endcap.
3. If replacing the bearing (F105), remove retaining ring (F110) using a retaining ring pliers.
4. Press on the inner race to remove the bearing (F105) from the shaft.
DDC20/24 shaft inspection
1. Ensure the shaft and its splines are straight and free of damage or heavy wear.
2. Inspect the shaft surface where it meets the shaft seal.
3. Replace the shaft if a groove exists at the sealing land surface that may let dirt into or hydraulic fluidout of the unit.
4. Clean the sealing area with a nonabrasive material if necessary.
5. Lubricate the shaft with a light coat of hydraulic fluid before assembly.

DDC20/24 shaft bearing inspection
1. Clean bearing with a solvent and lubricate with hydraulic fluid.
Replace the bearing if issues persist after cleaning.
2. Rotate the bearing in hand. The bearing should rotate smoothly.
3. Inspect for wear, or pitting.
If excessive wear is found, replace the bearing.

DDC20/24 shaft and seal assembly
1. Position the pump with the shaft end pointing up.
If previously removed; press bearing onto shaft by applying force to the inner race.
2. Lubricate and install bearing (F105) with hydraulic fluid.
3. Install retaining ring (F110) using retaining ring pliers.
4. Install shaft (F100) with bearing (F105) into housing. Ensure the shaft splines engage the block splines
and the shaft end slides smoothly into the rear bearing. It may be necessary to tap lightly on the shaft
to seat the bearing.

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DDC20/24 Axial Piston Pumps
Minor repair
5. Using retaining ring pliers, install the retaining ring (F115).
6. Cover shaft splines with an installation sleeve or packaging tape to protect seal during installation.
Lubricate new shaft seal (F120), press into housing until it bottoms out. Press evenly to avoid binding
and damaging the seal.

C Caution
Do not damage the housing bore, shaft or rear bearing when installing the shaft and shaft seal. Allcomponents should fit together smoothly.
7. Using retaining ring pliers, install the seal retaining ring (F125).
Install shaft /seal/bearing

F125

F120

F115

F110

F105

F100

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DDC20/24 Axial Piston Pumps
Minor repair
High pressure relief valve (HPRV)DDC20/24 high pressure relief valve (HPRV) removal
1. Mark the location of each valve for proper reassembly.
2. Remove the HPRV valve plugs (J140/J150).
3. Remove and discard O-rings (QJ020).
4. Use a magnet to remove the valves (N110/P110) and springs (N100/P100).
HPRV removal

QJ020

J150
P100
P110

N110
N100
J140

QJ020
P109625

HPRV plug
Item

Wrench size

TorqueJ140/J150

24 mm

78 N•m [57 lbf•ft]

DDC20/24 high pressure relief valve (HPRV) inspection
Inspect the plug and internal parts of cartridge. If parts are worn or damaged, replace the entire
cartridge.
DDC20/24 high pressure relief valve (HPRV) assembly
1. Lubricate and install new O-rings (QJ020) onto each plug (J140/J150).
2. Verify that the springs (N100/P100) are properly retained on the valves (N110/P110).
3. Install the valves (N110/P110) in their original location as noted during disassembly. Ensure eachvalve assembly moves freely in its bore.
4. Torque plugs per table.
5. Operate vehicle/machine through full range of controls to ensure proper operation. Check for leaks.

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DDC20/24 Axial Piston Pumps
Minor repair
Charge pressure relief valve (CPRV)DDC20/24 charge pressure relief valve (CPRV) removal
1. Remove the charge pressure relief valve plug (J320). Remove and discard O-ring (QJ040).
2. Use a magnet to remove the spring (L200).
3. Use a magnet to remove the charge relief poppet (L100).
DDC20/24 Charge pressure relief valve (CPRV) inspection
1. Inspect charge pressure relief valve (L100) for wear or damage.
2. Inspect spring (L200).
Replace any damaged components.
DDC20/24 charge pressure relief valve (CPRV) assembly
1. Lubricate and insert the charge relief valve poppet (L100) and spring (L200) into the endcap.
2. Lubricate and install a new O-ring (QJ040).
3. Install the charge relief valve plug (J320). Torque plug per table.

DDC20/24 Remove CPRV
J320
QJ040
L200
L100

Charge pressure relief valve plug

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Item

Wrench size

Torque

J320

17 mm

24 N•m [18 lbf•ft]

AX152986482107en-000503

Service Manual
DDC20/24 Axial Piston Pumps
Minor repair
Loop flushing valve
DDC20/24 loop flushing valve removal
1. Remove the loop flushing valve plugs (J220/J230). Remove and discard O-rings (J220A/J230A).
2. Use a magnet to remove the springs (H150) and spring guides (H200).
3. Use a magnet to remove the loop flushing spool (H100).
DDC20/24 loop flushing valve inspection
1. Inspect the springs (H150). Replace the springs if they are warped or bent.
2. Inspect the loop flush spool (H100), replace it if it is worn or damaged.
3. Inspect plugs (J220/J230) and spring guides (H200) for wear.
4. Install new O-rings (J220A/J230A) to plugs (J220/J230) before assembly.
DDC20/24 loop flushing valve assembly
1. Lubricate and insert the loop flushing spool (H100) into endcap.
Ensure the spool moves freely in its bore.
2. Install the spring guides (H200) and springs (H150).
3. Lubricate and install the O-rings (J220A/J230A) on the plugs.
4. Thread the loop flushing valve plugs (J220/J230) into the endcap and torque plugs per table.

DDC20/24 Remove loop flushing valve

J230
J230A

H150
H200

J220

H100
H200
H150 J220A

Loop flushing valve plugs© Danfoss | December 2023

Item

Wrench size

TorqueJ220/J230

11/16 inch

35 N•m [26 lbf•ft]

AX152986482107en-000503 | 23

Service Manual
DDC20/24 Axial Piston Pumps
Minor repair
Bypass valve
DDC20/24 bypass valve removal
1. Remove the bypass valve (M100).
2. Remove and discard the O‑rings (M130 and M110) and the backup ring (M120).
DDC20/24 bypass valve inspection
1. Inspect the valve. If the bypass valve (M100) is damaged, replace it.
2. Replace O-rings (M110 & M130) and back-up ring (M120) before assembly.
DDC20/24 bypass valve assembly
1. Lubricate and install new O-rings (M130 and M110) and backup ring (M120) onto cartridge.
2. Install the bypass valve (M100/M200). Torque valve per table.

DDC20/24 Remove bypass valve

M200
M100

M120

M120
M130
M130
M110
M110

Bypass valve plug

24 | © Danfoss | December 2023

Item

Wrench size

TorqueM100/M200

17 mm

12 N•m [9 lbf•ft]

AX152986482107en-000503

Service Manual
DDC20/24 Axial Piston Pumps
Minor repair
Optional coupling
DDC20/24 optional coupling removal
Remove the coupling (J538).
DDC20/24 coupling inspection
Inspect the coupling. If the coupling is damaged, replace it.
DDC20/24 coupling assembly
Lubricate and install the coupling (J538).

DDC20/24 Remove coupling

J538
Coupling

P108 580E© Danfoss | December 2023

AX152986482107en-000503 | 25

Service Manual
DDC20/24 Axial Piston Pumps
Torque charts
DDC20/24 charge pump fasteners and torque chart
Aux pad (left) and gerotor (right)
J550

J550

K200

Item

Fastener

Wrench size

TorqueK200

Charge pump cover
mounting bolt

6 mm internal hex

20 N•m [15 lbf•ft]

J550

Endcap/charge pump cover 8 mm internal hex
mounting bolts

39 N•m [29 lbf•ft]

DDC20/24 implement pump fasteners and torque chart
K210

K200

P10880326 | © Danfoss | December 2023

Item

Fastener

Wrench size

TorqueK200

Charge pump cover
mounting bolt

8 mm internal hex

60 N･m [44 lbf･ft]

K210

Endcap/implement pumphousing mounting bolt

8 mm internal hex

39 N･m [29 lbf･ft]

AX152986482107en-000503

Service Manual
DDC20/24 Axial Piston Pumps
Torque charts
DDC20/24 Gerotor- plug sizes and torque chart
L1

M3

J140

J320

M200
J220
MA

MB

L3

W Warning
Do not over torque the case drain plugs (L1, L2, L3)
Item

Plug

Port dimensions

Wrench size

TorqueJ140/J150
L1/L2/L3

HPRV

3/4-16 UNF

24 mm

78 N•m [57 lbf•ft]

Case drain

3/4-16 UNF

5/16 inch internal hex

29 N•m [21 lbf•ft]

J220/J230

Loop flushing valve plug

9/16-18 UNF

11/16 inch internal hex

35 N•m [26 lbf•ft]

M100/M200

Bypass valve

9/16-18 UNF

17 mm

12 N•m [9 lbf•ft]

J320

CPRV

1/2-20 UNF

17 mm

24 N•m [18 lbf•ft]

MA/MB

System Pressure Gauge Ports 9/16-18 UNF

11/16 inch

35 N•m [26 lbf•ft]

M3

Charge Pressure Gauge Port

3/16 inch internal hex

19 N•m [14 lbf•ft]© Danfoss | December 2023

7/16-20 UNF

AX152986482107en-000503 | 27

Service Manual
DDC20/24 Axial Piston Pumps
Torque charts
DDC20/24 aux pad plug sizes and torque chart
M3
L1
J320

J140

J220

M100

M3/ E
L2

J150

MA

J230

MB
L3

W Warning
Do not over torque the case drain plugs (L1, L2, L3).
Item

28 | © Danfoss | December 2023

Plug

Port dimensions

Wrench size

TorqueJ140/J150

HPRV

3/4-16 UNF

24 mm

78 N•m [57 lbf•ft]

M3/E

Charge gauge/
Charge inlet

9/16-18 UNF

1/4 inch internal hex

35 N•m [26 lbf•ft]

L1/L2/L3

Case drain

3/4-16 UNF

5/16 inch internal hex 30 N•m [22 lbf•ft]

J220/J230

Loop flushing valveplug

9/16-18 UNF

11/16 inch internalhex

35 N•m [26 lbf•ft]

M100/M200

Bypass valve

9/16-18 UNF

17 mm

12 N•m [9 lbf•ft]

J320

CPRV

1/2-20 UNF

17 mm

24 N•m [18 lbf•ft]

MA/MB

System Pressure
Gauge Ports

9/16-18 UNF

11/16 inch

35 N•m [26 lbf•ft]

AX152986482107en-000503

Service Manual
DDC20/24 Axial Piston Pumps
Torque charts
DDC20/24 implement pump plug sizes and torque chart
L1

M3/E

M3/ E

J140
J320

M200
L2

D
J150

MA

MB

L3

W Warning
Do not over torque the case drain plugs (L1, L2, L3).
Item

Plug

Port dimensions

Wrench size

TorqueJ140/J150

HPRV

3/4-16 UNF

24 mm

78 N•m [57 lbf•ft]

M3/E

Charge gauge/Implement
return

9/16-18 UNF

1/4 inch internal hex

35 N•m [26 lbf•ft]

L1/L2/L3

Case drain

3/4-16 UNF

5/16 inch internal hex

29 N•m [21 lbf•ft]

M200

Bypass valve

9/16-18 UNF

17 mm

12 N•m [9 lbf•ft]

J320

CPRV

1/2-20 UNF

17 mm

24 N•m [18 lbf•ft]

MA/MB

System Pressure Gauge Ports 9/16-18 UNF

11/16 inch

35 N•m [26 lbf•ft]

D

Implement discharge

1/4 inch internal hex

35 N•m [26 lbf•ft]© Danfoss | December 2023

9/16-18UNF

AX152986482107en-000503 | 29

Products we offer:

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Cartridge valves
DCV directional control
valvesElectric converters
Electric machines

Danfoss Power Solutions is a global manufacturer and supplier of high-quality hydraulic andelectric components. We specialize in providing state-of-the-art technology and solutions
that excel in the harsh operating conditions of the mobile off-highway market as well as themarine sector. Building on our extensive applications expertise, we work closely with you toensure exceptional performance for a broad range of applications. We help you and othercustomers around the world speed up system development, reduce costs and bring vehicles
and vessels to market faster.

Gear motors

Danfoss Power Solutions – your strongest partner in mobile hydraulics and mobile
electrification.

Gear pumps

Go to www.danfoss.com for further product information.

Hydraulic integrated
circuits (HICs)
Hydrostatic motors

We offer you expert worldwide support for ensuring the best possible solutions foroutstanding performance. And with an extensive network of Global Service Partners, we also
provide you with comprehensive global service for all of our components.

Electric motors

Hydrostatic pumps
Orbital motors
PLUS+1® controllers
PLUS+1® displays
PLUS+1® joysticks andpedals
PLUS+1® operator
interfaces
PLUS+1® sensors
PLUS+1® software
PLUS+1® software services,support and training
Position controls andsensors
PVG proportional valves
Steering components andsystems
Telematics

Local address:

Hydro-Gear
www.hydro-gear.com
Daikin-Sauer-Danfoss
www.daikin-sauer-danfoss.com

Danfoss
Power Solutions (US) Company
2800 East 13th Street
Ames, IA 50010, USA
Phone: +1 515 239 6000

Danfoss
Power Solutions GmbH & Co. OHG
Krokamp 35
D-24539 Neumünster, Germany
Phone: +49 4321 871 0

Danfoss
Power Solutions ApS
Nordborgvej 81
DK-6430 Nordborg, Denmark
Phone: +45 7488 2222

Danfoss
Power Solutions Trading(Shanghai) Co., Ltd.
Building #22, No. 1000 Jin Hai Rd
Jin Qiao, Pudong New District
Shanghai, China 201206
Phone: +86 21 2080 6201

Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products
already on order provided that such alterations can be made without subsequent changes being necessary in specifications already agreed.
All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.

© Danfoss | December 2023

AX152986482107en-000503