11-53
5540F/YB5515 SERVICE MANUAL STRUCTURALS
Mast Bearing Bolts
Very high stress is put on the mast bolts during crane
operation. It is important that these bolts be checked at
regular intervals.
Check the torque on the bolts after the first week or 50 hours
of operation, whichever occurs first, and then every month or
250 hours of operation, whichever occurs first. Make a
record of any loose bolt. If any bolt does not hold to correct
torque after the second check, remove and replace the bolt.
A loose bolts indicates possible failure of the bolt.
The correct torque on each outside bolt (mast to swing
bearing) should be 159 lb-ft. (216 Nm). The correct torque on
each inside bolt (swing bearing to frame) should be 282 lb-ft.
(384 Nm).
Use the torque sequence shown in Figure 11-123 when
check the torque on the bolts.
NOTE: Use only special Grade 8 bolts for replacement of
the mast bolts. Order the bolts from your Grove
dealer, see your parts manual.
NOTE: If a broken bolt is found, replace the bolt and also
replace the bolt on each side of the broken bolt.
NOTE: The proper torque will not be obtained without the
hardened steel washers under the bolt heads on
the outer (mast) bolt circle.
Inspection For Bearing Wear
Because of conservative design parameters, static loading
and slow intermittent rotation, there are very few mast
bearings that ever see their full design use.
However, the mast bearing does have moving internal parts
that are prone to wear if not maintained properly. As the
bearing wears, there will be free-play or movement in the
bearing.Some of the symptoms of mast bearing wear are:
a. Metal particles in the grease around the seal.
b. Increased drive power required.
c. Noisy rotation.
d. Rough rotation.
If one or more of the above symptoms are present, the
following procedure should be used to test the bearing for
excessive wear.
1. On a level, hard packed surface, set the machine up on
its outriggers.
2. With the boom forward, fully extended and in a
horizontal position, place a dial indicator on the swing
gearbox cover and mast as shown in Figure 11-124.
3. Set the dial indicator to zero.
4. Raise the boom to its full raised position and record the
amount of movement on the dial indicator.
5. Lower the boom and then rotate it 180°. Repeat steps 2
though 4.
6. Average the two readings. The maximum allowable
movement is 0.060 inches (1.52 mm). The mast bearing
must be replaced if the movement is greater than the
stated measurement.
Replacing The Mast Bearing
Removal
1. Refer to boom removal in this section and remove the
boom from the mast.
2. Remove swivel stop (25, Figure 11-125) from the bottom
of the hydraulic swivel 26.
3. Attach tags to the hydraulic hoses and lines with the
swivel port number to which they connect.
FIGURE 11-123
a0495
Swing Mechanism
Reference Only
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