DETROIT DIESEL 53
shafts with the missing serrations in alignment with
the missing serrations on the shafts.
9. Tap the gears lightly with a soft hammer to seat
them on the shafts. Then rotate the gears until the
punch marks on the face of the gears match. If the
marks do not match, re-position the gears.
10. Wedge a clean cloth between the blower rotors.
Use the gear retaining bolts and plain washers to press
the gears on the rotor shafts (Fig. 13). Turn the bolts
uniformly until the gears are tight against the
shoulders on the shafts.
11. Remove the gear retaining bolts and washers. Then
proceed as follows:
3-53 Blower-- Place the gear washers on the
gears and start the gear retaining bolts in the rotor
shafts. Tighten the bolts IO 25-30 lb-ft torque.
Fig. 16 - Measuring Rotor Lobe to End Plate
bolts and plain washers
12. Check the backlash between the blower gears,
using a suitable dial indicator. The specified backlash
6. Attach the two thrust washers to the front end of the
is .0005" to ,0025" with new gears or a maximum of
blower with the washer retaining bolts. If 5/16 "-24
.0035" with used gears.
bolts are used, tighten them to 25-30 lb-ft torque; if
3 / 8 " - 24 bolts are used. tighten them to 54-59 lb-ft
13. Time Blower Rotors
After the blower rotors and gears have been installed,
the blower rotors must be timed. When properly
7. Attach the three spacers and the thrust plate to the
positioned, the blower rotors run with a slight
front end of the blower. Tighten the three bolts to 7-9
clearance between the rotor lobes and with a slight
lb-ft torque. Then check the clearance between the
clearance between the lobes and the walls of the
thrust plate and the thrust washers. The specified
clearance is .001" to .003"
The clearances between the rotors may be established
NOTE: The current thrust plate is .260" thick.
by moving one of the helical gears out or in on the
The former plate was .180" thick.
shaft relative to the other gear by adding or removing
shims between the gear hub and the rotor spacers.
8. Position the rotors so that the missing serrations on
the gear end of the rotor shafts are 90° apart. This is
It is preferable to measure the clearances with a feeler
accomplished by placing the rotors in a "T" shape,
gage comprised of two or more feelers, since a
with the missing serration in the upper rotor facing to
combination is more flexible than a single feeler gage.
the left and the missing serration in the lower rotor
Take measurements from both the inlet and outlet
facing toward the bottom (Fig. 14). Install the shims
sides of the blower.
and spacers in the counterbore in the rear face of the
a. Measure the clearance between the rotor lobes and
rotor gears. Then place the gears on the ends of the
SEC. 3.4 Page 9