PRIORITY - THE CENTER DRIVE SHAFT BEARINGS NEED TO BE INSPECTED FOR CORRECT ADJUSTMENT ON CERTAIN 518 AND 528 SKI DDERS - PI3479 - MAILED US AND CANADA, CACO, COSA, LIMITED COFA Caterpillar

U-168
A-115
AU-108.1
O-128
PRIORITY
3253  PI3479
COMPLETION DATE  

February 28, 1991  August 31, 1991

The bearings on the center drive shaft, inside the oscillating hitch, may not
have been adjusted correctly. This can result in a low hour bearing and
shaft failure with possible damage to the hitch.

Model Identification Number
518  94U2257-2302
95U2682-2773, 2775-2781, 2783-2786, 2788
528  96C720-740
97C376-387

Dealers will need to order parts for this Program.
***** 518 Skidders *****
1 - 7K5425 Shim
1 - 0S1922 Lock
***** 528 Skidders *****
1 - 4K7294 Lock
1 - 8K5892 Shim

See the attached procedure.

U.S. and Canadian owners will receive the attached Owner Notification.

***** Machines Being Checked In The Field *****
Caterpillar Dealer Suggested Customer Suggested
Parts Labor Hrs. Parts Labor Hrs. Parts Labor Hrs.
(D/N) (Sell)  (C/L) (Sell)
100% 3 0 0  0 0
NOTE: This is a 3 hour job.
***** Machines In Dealer Inventory *****
Caterpillar Dealer Suggested Customer Suggested
Parts Labor Hrs. Parts Labor Hrs. Parts Labor Hrs.
(D/N) (Sell)  (C/L) (Sell)
100% 2 0 0  0 0
NOTE: This is a 2 hour job.

Any parts removed (with the exception of cores used for Caterpillar
Remanufactured parts) can be rendered useless and scrapped immediately upon
completion of the repair.
MAKE EVERY EFFORT TO COMPLETE THIS PROGRAM AS SOON AS POSSIBLE.
Attach. (1-Owner Notification)
(2-Rework Procedure)
COPY OF 

 FOR U.S. AND CANADIAN OWNERS
XYZ Corporation
3240 Arrow Drive
Anywhere, YZ 99999
PRIORITY - The Center Drive Shaft Bearings Need To Be Inspected
For Correct Adjustment On Certain 518 And 528
Skidders
MODELS INVOLVED - 518 and 528 Skidders
Dear Caterpillar Product Owner:
The bearings on the center drive shaft, inside the oscillating hitch, need to
be inspected for correct adjustment on the products listed below. The repair
will be done at no cost to you.
Contact your local Caterpillar dealer immediately and schedule a time to have
this service performed. The repair time for this service is approximately
three hours.
We regret the inconvenience this may cause you, but urge you to have this
service performed as soon as possible to prevent unscheduled downtime.
Caterpillar Inc.
Identification #(s)
Attached to August 16, 1990 Service Letter
Rework Procedure
1. Follow the procedures in the Disassembly and Assembly section of the
Service Manual. If the retaining plate on the rear of the hitch is
going to be removed, the front and rear of the machine must be supported
as described in the Service Manual.
2. Remove the rear frame bottom guard.
3. Remove the drive shaft that connects the center drive line to the rear
axle.
4. Remove the splined sliding drive shaft which connects the center drive
line to the front of the machine. This will permit free movement of the
center drive shaft within the oscillating hitch.
5. Measure the shaft endplay using a dial indicator with a magnetic base.
Move the center drive shaft using a pry bar while measuring the actual
endplay. If the endplay is with the following specifications, no other
work is necessary. Go to Step 7 to assemble the machine.
Model Specifications
518  0.05 - 0.10 mm (.002 - .004")
528  0.03 - 0.08 mm (.001 - .003")
6. If there is excessive endplay (shims have to be removed), adjust the
endplay to the specifications given in Step 5.
If there is bearing preload and no endplay (shims have to be added), use
one of the following steps:
A. If the machine is in dealer inventory with very low service hours,
make an over-all visual inspection, including the outside of the
hitch and seal areas for any signs of heat. Rotate the shaft to
check for any rough areas. If problems are not evident, adjust the
bearing to the specified bearing clearance.
B. If the machine has been put into service and has been operated,
look for signs of heat in the hitch area such as grease being
thrown out around the shaft. Also, inspect the lip of the 6V3261
Seal (on the 518 Skidder) or 7K5191 Seal on the 528 Skidder for
damage caused by heat. (This seal is located in the hitch bore at
the center side of the hitch). Excessive heat in this area may also
result in a burned grease odor. If there are any signs of
excessive heat, the center drive shaft should be removed and the
bearings replaced.
a) If there are no signs of excessive heat, further inspection is
necessary. Install a straight grease fitting, such as a 3B8489
Fitting or a 6L3616 Adapter, in place of the 3B8485 Fitting (518)
and 3B8486 Fitting, on the 528 Skidder, located in the hitch pin
end of the drive shaft. This will permit the use of a socket wrench
to rotate the drive shaft.
b) Use an inch-pound torque wrench with a dial to measure the rolling
torque of the center drive shaft. Record the reading.
A drive shaft with endplay that has been correctly adjusted will
require about 30 inch-pounds of torque to rotate the shaft
smoothly. If the torque required to turn the shaft is not uniform,
or the shaft rotation feels rough, the drive shaft should be
removed and the bearings replaced.
c) If the shaft rotates smoothly, shim the shaft assembly to obtain
the correct endplay measure the rolling torque of the shaft.
Compare the rolling torque with the correct endplay to the initial
rolling torque.
If the rolling torque has decreased by 30 inch-pounds or less, the
bearings have not been damaged due to excessive preload. The
machine can be assembled. Example: The rolling torque initially
measured 45 inch-pounds and then measured 30 inch-pounds after the
endplay was adjusted is a decrease of 15 inch-pounds.
If the rolling torque has decreased by more than 30 inch-pounds
after the endplay has been correctly adjusted, there is a high
probability of decreased bearing life and the center drive shaft
bearings should be replaced. Example:
The rolling torque initially measured 150 inch-pounds and then
dropped to 35 inch-pounds after the endplay was adjusted. This is
a decrease of 115 inch-pounds.
d) Install the original 3B8485 or 3B8486 Grease fitting .
7. Install the splined sliding shaft into the center of the machine
and tighten the coupling bolts to the specified torque.
8. Install the drive line connecting the center shaft to the rear axle
and tighten the bolts to the specified torque.
9. Install the bottom guards and tighten the bolts to the specified
torque. Tighten the bolts to the specified torque twice to prevent
the bolts from coming loose and causing damage to the bolts and
bottom guard. The specified torques for the bolts are:
5/8" Bolt - 170 lb ft.
3/4" Bolt - 300 lb ft.