18
field repair
e–The difference in dial indicator readings (steps c and d) is
the initial fan shaft bearing end play. In order to achieve the
prescribed preload of .001 to .002" (.025–.051mm) remove
an amount of shims from between the case and bottom cap
equal to the measured end play plus .000 to .002". For ex-
ample if the measured end play is .005" (.127mm), remove
a total of .005 to .007" (.127–.177mm) in shim thickness.
Caution–If Geareducer is in the upright position when bottom
cap is removed, block under the ring gear to prevent gear
from dropping down onto lower interstage bearing retainer
(roller cage).
9. Install O-ring in bottom cap and install bottom cap. Tighten
cap screws to 80 ft·lbƒ (109 N·m) torque.
10. a–Coat labyrinth recess in case cover with Permatex No. 2
and install labyrinth ring.
b–Fill grooves of labyrinth ring and water slinger with lithium-
base grease of NLGI No. 2 consistency.
11. Install water slinger and its O-ring (703) on fan shaft.
12. Install inspection cover, gasket (602), and drain plug.
POINT OF NORMAL
BACKLASH MEASUREMENT
Figure 16
Gear Backlash Measurement
Gear Setting Procedure
Part numbers and references—refer to
Figures 3, 4 and 16.
The proper mounting of the gear set is essential to obtain long
life and smooth operation of the gears. The pinion cage position
adjustment is obtained by shims under the flange of the pinion
cage. Shims are placed under the top interstage bearing cap to
adjust ring gear position. The gear setting may require several
attempts before obtaining the proper backlash and tooth contact
pattern.
The gear and pinion are match-marked when lapped and must be
assembled the same way. The ring gear has the end of two teeth
marked "X" and the pinion has one tooth so marked—the gears
should be engaged with the X-marked pinion tooth between those
marked on the ring gear. Match marks can be checked through
the inspection opening.
With the marked teeth of the gear engaged, check backlash
with dial indicator—see Figure 16. The indicator can be installed
through the inspection cover opening. Change shims under top
interstage bearing cap until backlash is between .007–.009"(.178–
.228mm) normal to ring gear tooth.
With gears adjusted for proper backlash, blue (Prussian Blue in
oil) the gear teeth. Drive the pinion by turning ring gear in both
directions for several revolutions. Observe the contact pattern
on both gears on both sides of the teeth. The contact pattern
should be as shown in Figure 17.
If correct tooth contact pattern is not obtained on first attempt,
refer to Figure 17—these illustrations show the two cases of
“out-of- position contact” in the extreme. One of the remedies
indicated will correct the out-of-position contact—compare the
tooth contact pattern with the illustrations in Figure 17 and
choose the required remedy.
When proper tooth contact has been obtained, recheck the back-
lash at marked teeth. If it is within the desired range—.007–.009"
(.178–.228mm), check backlash with dial indicator at two ad-
ditional points 120° apart (with inspection cover removed), and
as shown in Figure 16. All backlash readings must be within the
specified range. If backlash is not within the limits, adjust ring gear
height with shims until it is, checking again as described.
