725C, 725C2, 730C and 730C2 Articulated Truck Systems Caterpillar

Suspension Height (Front) - Check and Adjust

Usage:

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Personal injury or death can result from sudden suspension cylinder movement.
Sudden movement, up or down, can cause the clearance above your head to change rapidly.
Read all warning labels on the suspension cylinders before servicing. Do not check the oil in the suspension cylinder until all the nitrogen pressure has been released.
Do not, under any condition, remove valves, cover or plugs from the cylinder unless the rod is fully retracted and all the nitrogen pressure is released.

Do not stand under the machine when testing or adjusting the suspension cylinders.

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Dry nitrogen is the only gas approved for use in the suspension cylinders. Charging the suspension cylinders with oxygen gas will cause an explosion. This danger will not happen if nitrogen cylinders with standard CGA (Compressed Gas Association, Inc.) Number 580 Connections are used.
When you order nitrogen gas, be sure that the cylinders are equipped with CGA No. 580 Connections. Do not use color codes or other methods of identification to tell the difference between nitrogen cylinders and oxygen cylinders.

Never use an adapter to connect your nitrogen charging group to a valve outlet used on both nitrogen, oxygen or other gas cylinders. Be sure you use dry nitrogen (99.8% purity).

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When the suspension is lowered clearances between the machine frames and suspension components are reduced.
Persons on or near the machine could be injured by crushing.

Keep all personnel clear of the machine until the suspension has been lowered.

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NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat^® products. Dispose of all fluids according to local regulations and mandates.

Specifications

Use TDTO 10 W oil in the quantity that is specific to the machine when rebuilding or assembling a suspension cylinder. Refer to Table 1.

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Table 1
Oil Capacity For Suspension Cylinders
Model	Capacity
725, 725C, 725C2, 730, 730 Ejector, 730C, 730C Ejector, 730C2, 730C2 EJ	4 L (1.0568 US gal)
735, 740, 740 Ejector, 735C, 745C, 740C Ejector, 740, 745	3.92 L (1.0355 US gal)

Note: When you are charging the suspension cylinder with oil, use TDTO 10 W oil and add 1U-9891 Hydraulic Oil Additive. The ratio of additive to oil is 12.5 ml per 1 L (0.2642 US gal).

After the suspension cylinder contains the required amount of oil, install the suspension cylinder. After this installation has been done, normal charging procedures can be performed.

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Table 2
Suspension Measurements
Model	Measurement	Actual
725, 725C, 725C2, 730, 730 Ejector, 730C, 730C Ejector, 730C2, 730C2 EJ	Machine Rim to Fender Measurement (AA) ⁽¹⁾	Left
	Machine Rim to Fender Measurement (AA) ⁽¹⁾	Right
	Target Length of Cylinder Extension for Correct Suspension Height (BB) ⁽²⁾	95 ± 10 mm (3.7 ± 0.4 inch)
	Pin-to-Pin Measurement of Fully Retracted Cylinder (CC) ⁽²⁾	615 mm (24 inch)
	Pin-to-Pin Measurement at the Correct Suspension Ride Height (Stroke Midpoint) (DD) ⁽²⁾	710 ± 10 mm (28 ± 0.4 inch)
735, 740, 740 Ejector, 735C, 745C, 740C Ejector, 740, 745	Machine Rim to Fender Measurement (AA) ⁽¹⁾	Left
	Machine Rim to Fender Measurement (AA) ⁽¹⁾	Right
	Target Length of Cylinder Extension for Correct Suspension Height (BB) ⁽²⁾	75 ± 10 mm (3.7 ± 0.4 inch)
	Pin-to-Pin Measurement of Fully Retracted Cylinder (CC) ⁽²⁾	625 mm (24.6 inch)
	Pin-to-Pin Measurement at the Correct Suspension Ride Height (Stroke Midpoint) (DD) ⁽²⁾	700 ± 10 mm (27 ± 0.4 inch)

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⁽¹⁾	Refer to Illustration 15 for measurement details
⁽²⁾	Refer to Illustration 16 for measurement details

References

Note: A CWS login is required to access Caterpillar Channel1. Scan the QR code below with a QR enabled device or copy the link that follows.

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Illustration 1	g06281999

Reference: For more information, refer to “Articulated Truck Suspension Height (Front) – Check and Adjust” on Caterpillar Channel1.

https://channel1.mediaspace.kaltura.com/media/Articulated+Truck+Suspension+Height+%28Front%29+%E2%80%93+Check+and+Adjust/1_2lx1ktu8

Introduction

This procedure includes the following procedures:

Lowering the Suspension
Purging the Suspension Cylinder
Nitrogen Charging Procedure - Setting the Suspension Ride Height

Note: Both suspension cylinders must be charged at the same time. If only one suspension cylinder needs servicing, perform the procedure on both suspension cylinders.

Required Tools

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Illustration 2	g06237587

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Table 3
Tooling (T1) 175-5507 Nitrogen Charging
Tool	Item	Qty	Part No	Description
T1	A	1	162-4147	Hose As
	B	2	8S-4600	Fitting
	C	2	8S-1506	Coupling As
	D	1	162-4146	Regulator
	E	2	8T-0859	Pressure Gauge
	F	1	8S-4599	Coupling As
	G	1	2S-5244	Fitting
	H	1	1S-8937	Needle Valve
	J	1	2D-7325	Pipe Tee
Tooling (T2) 175-7410 Nitrogen Charging Fitting Group
Tool	Item	Qty	Part No	Description
T2	A	2	8S-7169	Coupling
	B	2	1S-8941	Hose As
	C	2	7S-5106	Chuck
	C ⁽¹⁾	2	1S-8938	Chuck
	D	2	175-6857	Hose As
	E	1	2D-7325	Pipe Tee
	F	2	1S-8937	Needle Valve
	G	2	5P-8998	Fitting
	H	1	3D-8884	Elbow

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⁽¹⁾	Not part of 175-7410 Nitrogen Charging Fitting Group. 1S-8938 Chuck is required on machines equipped with Type 2 and Type 3 charging valves.

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Illustration 3	g06237578
Tooling (T3) 9U-5617 Oil Refill Pump

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Table 4
Tooling (T3) 9U-5617 Oil Refill Pump
Tool	Item	Qty	Part Number	Part Description
T3	1	1	9U-5617	Oil Refill Pump

Check Preparation

Move the machine to a smooth, horizontal location that is away from operating machines and away from personnel.
Permit only one operator on the machine. Keep all other personnel away from the machine or in the operator sight.
Rotate the steering wheel to a NEUTRAL position.
Move the transmission control to the neutral position and depress the front of the parking brake control switch to engage the parking brake.
Note: The parking brake is engaged by moving the transmission control to the park position on 740 and 745 Articulated Trucks.
Lower or retract the implements.
Stop the engine.
Ensure that the pressure is released from any closed system that will be opened during the maintenance procedure. Refer to the machine Operation and Maintenance Manual, "System Pressure Release" for more information.
Install the steering lock and chock the wheels.
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Illustration 4 g06195159

Top view of the suspension group
(1) Suspension Group

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Illustration 5 g06195190

Suspension cylinder with charging valve
(1) Suspension Group
(2) Cover
(3) Charging Valve (Type 3)
(3A) Nut
Locate front suspension group (1).

Note: The following procedures demonstrate how to properly lower, purge and charge a machine equipped with Type 3 charging valves on the suspension cylinders. Type 3 charging valves incorporate an additional valve which must be opened and closed by rotating nut (3A). Some steps in this procedure may differ based on which charging valves are installed on the suspension cylinders. For additional information on charging valves and how to identify which charging valve is installed on your machine, refer to REHS5464, "Accumulator Discharging and Charging Procedures".

Opening the Charging Valve

Fully rotate the T-Handle on each chuck (T2C) counter clockwise and turn needle valves fully clockwise to ensure that all charging equipment is closed.
Install chuck (T2C) onto the charging valve.
Rotate nut (3A) counterclockwise two full turns to open the charging valve.
Turn the T-Handle on chuck (T2C) clockwise to open the charging valve.

Closing the Charging Valve

Turn T-Handle on chuck (T2C) counterclockwise to close the charging valve.
Rotate nut (3A) clockwise to close the charging valve. Tighten the nut to 7 ± 1 N·m (62 ± 9 lb in).
Note: It is important to follow the procedure and use the appropriate torque specifications on nut (3A) when closing the charging valves. Over tightening nut (3A) may result in a cracked or damaged valve.

Lowering the Suspension

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Illustration 6	g06234835
Suspension group orientation view (1) Suspension Group (4) Charging Valve (5) Charging Valve (6) Air Bleed Valve

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Illustration 7	g06234822
Suspension group detailed charging valve view (1) Suspension Group (4) Charging Valve (5) Charging Valve

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Illustration 8	g06235888
Suspension group detailed air bleed valve view (1) Suspension Group (6) Air Bleed Valve

Remove the cover which protects charging valve (4) (left) and charging valve (5) (right). Remove the valve cap from charging valve (5) that is on top side of the suspension cylinders. Before installing Tooling (T2), turn the T-Handle on chuck (2TC) counterclockwise to ensure that the charging valve will not open during installation. Make sure that the needle valve on the opposite end is fully closed. Install Tooling (T2) with the chuck on charging valve (5) and the needle valve into a suitable approved container.
Rotate nut (3A) on charging valve (5) counterclockwise two full turns to open the charging valve.
Turn the T-Handle on chuck (T2C) clockwise to open charging valve (5).
Note: The machine will settle slightly as the hose assembly is filled with nitrogen.
Move away from the machine before performing this step. Open the needle valve and allow the nitrogen to flow into the suitable container. When the suspension cylinder has bottomed completely, leave the tooling in position for 5 minutes. Leaving the tooling in position for 5 minutes will allow the pressure in the suspension cylinder to equalize.
Turn T-Handle on chuck (T2C) counterclockwise to close charging valve (5).
Rotate nut (3A) on charging valve (5) clockwise to close the charging valve.
Remove Tooling (T2) from charging valve (5).
Remove the valve cap from air bleed valve (6). Before installing Tool (T2), turn the T-Handle on chuck (T2C) counterclockwise to ensure that the charging valve will not open during installation. Make sure that the needle valve on the opposite end is fully closed. Install Tooling (T2) with the chuck on air bleed valve (6) and the needle valve into a suitable approved container.
Rotate nut (3A) on air bleed valve (6) counterclockwise two full turns to open the valve.
Turn the T-Handle on chuck (T2C) clockwise to open air bleed valve (6).
Move away from the machine before performing this step. Open the needle valve and allow the nitrogen to flow into the suitable container. Leave the tooling in position for 5 minutes. Leaving the tooling in position for 5 minutes will allow the pressure in the suspension cylinder to equalize.
Turn T-Handle on chuck (T2C) counterclockwise to close charging valve (6).
Rotate nut (3A) on charging valve (6) clockwise to close the charging valve.
Remove Tooling (T2) from charging valve (6).

Note: Perform the "Lowering the Suspension" section on both sides of the machine prior to moving on to the "Purging the Suspension Cylinder" section.

Purging the Suspension Cylinder

Note: Verify that all steps from "Lowering the Suspension" have been performed prior to attempting the purge the cylinders.

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Illustration 9	g06234835
Suspension group orientation view (1) Suspension Group (4) Charging Valve (5) Charging Valve (6) Air Bleed Valve

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Illustration 10	g06234822
Suspension group detailed charging valve view (1) Suspension Group (4) Charging Valve (5) Charging Valve

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Illustration 11	g06235888
Suspension group detailed air bleed valve view (1) Suspension Group (6) Air Bleed Valve

Remove the valve cap from charging valve (4).
Install Tooling (T3) to charging valve (4) and Tooling (T2) to air bleed valve (6).
Note: Before installing Tooling (T3) and Tooling (T2), turn the T-Handle on chucks (T2C) counterclockwise to ensure that the charging valves will not open during installation. Make sure that the needle valve on the opposite end is fully closed.
Use Tooling (T3) to inject oil into the suspension cylinder. The oil will flow through charging valve (4) and out air bleed valve (6) and Tooling (T2) into a suitable container.
When the oil that is flowing out of the suspension cylinder is clean and free of air, stop Tooling (T3).
Turn the T-Handle on chuck (T2C) at air bleed valve (6) counterclockwise to close the chuck.
Rotate nut (3A) on air bleed valve (6) clockwise to close the valve and remove Tooling (T2).
Install Tooling (T2) with chuck (T2C) on charging valve (5) and the needle valve into a suitable approved container.
Note: Before installing Tooling (T2) on charging valve (5), turn the T-Handle on chuck (T2C) counterclockwise to ensure that the charging valve will not open during installation. Make sure that the needle valve on the opposite end is fully closed.
Rotate nut (3A) counterclockwise two full turns to open charging valve (5).
Turn the T-Handle on chuck (T2C) clockwise to open up the charging valve. Open the needle valve into the suitable container.
Use Tooling (T3) to inject oil into the suspension cylinder. The oil will flow through charging valve (4) and out charging valve (5) and Tooling (A) into a suitable container.
When the oil that is flowing out of the suspension cylinder is clean and free of air, stop Tooling (T3).
Turn the T-Handle on chucks (T2C) at charging valve (5) and charging valve (4) counterclockwise to close the chuck.
Rotate nuts (3A) on charging valve (5) and charging valve (4) clockwise to close the valve and remove Tooling (T2) and Tooling (T3).
Install Tooling (T2) on charging valve (4) with the chuck on the charging valve and the needle valve into a suitable approved container.
Note: Before installing Tool (T2) to charging valve (4), turn the T-Handle on chuck (T2C) counterclockwise to ensure that the charging valve will not open during installation. Make sure that the needle valve on the opposite end is fully closed.
Rotate nut (3A) counterclockwise two full turns to open charging valve (4).
Turn the T-Handle on chuck (T2C) clockwise to open the charging valve. Open the needle valve into the suitable container.
Install Tooling (T1) onto charging valve (5).
Note: Before installing Tool (T1) to charging valve (5), turn the T-Handle on chuck (T2C) counterclockwise to ensure that the charging valve will not open during installation. Make sure that the needle valve on the opposite end is fully closed.
Rotate nut (3A) counterclockwise two full turns to open charging valve (5).
Adjust the regulated pressure to 689.5 kPa (100 psi) on the nitrogen cylinder.
Open the needle valve on Tooling (T1) and allow nitrogen to flow through the charging valve and into the suspension cylinder. A small amount of oil will flow out of Tooling (T2) and into the suitable container.
Eventually the flow of oil will stop and only nitrogen will flow through Tooling (T2). Turn the T-Handle on chuck (T2C) at charging valve (5) and charging valve (4) counterclockwise. Doing so will close the charging valve to stop the flow of nitrogen.
Rotate nut (3A) clockwise at charging valve (4) and charging valve (5) to close the charging valve.
Remove Tooling (T1) and Tooling (T2).

Nitrogen Charging Procedure - Setting the Suspension Ride Height

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Illustration 12	g06234835
Suspension group orientation view (1) Suspension Group (4) Charging Valve (5) Charging Valve (6) Air Bleed Valve

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Illustration 13	g06234822
Suspension group detailed charging valve view (1) Suspension Group (4) Charging Valve (5) Charging Valve

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Illustration 14	g06235888
Suspension group detailed air bleed valve view (1) Suspension Group (6) Air Bleed Valve

Remove cover (2) which protects charging valve (4) (left) and charging valve (5) (right) on both suspension cylinders.
Remove the valve cap from charging valve (5) on each suspension cylinder and connect Tooling (T2) with chuck (T2C).
Note: Before installing Tooling (T1) and Tooling (T2), turn the T-Handle on chuck (T2C) counterclockwise. Turning the T-Handle counterclockwise will ensure that the charging valves will not open during installation. Make sure that the needle valves on the opposite ends are fully closed.
Rotate nut (3A) counterclockwise two full turns to open charging valve (5).
Open the T-Handle on chuck (T2C) by turning the T-Handle clockwise. Connect (T1) to the nitrogen cylinder for charging.
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Illustration 15 g06234842
Measure Dimension (AA) on both sides of the machine. Dimension (AA) is the distance from the top of the rim to the bottom of the fender.
Note: Dimension (AA) will be different for each side of the machine. Record this number for both sides of the machine.
Adjust the regulated pressure to 10342 kPa (1500 psi) on the nitrogen cylinder.
Open the main needle valve (T1H) to allow the nitrogen flow into the two needle valves (TF2) for the left and right suspension cylinders. Slowly open the left needle valve which is in line to the suspension cylinder on the left side. Raise the machine approximately 10 mm (0.40 inch) and then close needle valve (TF2) for the left side.

Slowly open the right needle valve which is in line to the suspension cylinder on the right side. Raise the machine approximately 10 mm (0.40 inch) and then close needle valve (TF2) for the right side.

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Illustration 16	g06197606
Typical view of the suspension group retracted (left) and extended to the stroke midpoint (right) (BB) 75 ± 10 mm (3 ± 0.4 inch) (CC) 625 mm (24.6 inch) (DD) 700 mm (27.6 inch)

Alternate between the needle valve for the left and right side to allow the suspension to rise in increments of 10 mm (0.40 inch) until the correct suspension ride height is achieved. The correct suspension height will be dimension (AA) plus dimension (BB). Refer to Illustration 15, Illustration 16, and Table 2 for details.
Close main needle valve (TH1) to stop the flow of nitrogen to needle valves (TF2).
Turn the T-Handle on chuck (T2C) counterclockwise to close charging valve (5).
Rotate nut (3A) clockwise to close the charging valve.
Remove Tooling (T1) and Tooling (T2).
Operate the machine for several load cycles after the suspension has been properly charged. Recheck the ride height of the suspension. If necessary, adjust the height of the suspension.