CRANKSHAFT
.
-
.
3/16" (4.763
mrn)
TO
BE
SHOT- PEENED
4
ONANNO.
//
420-0275
.
FIGURE
115.
REMOVING
CRANKSHAFT GEAR
Removal
1.
2.
3.
4.
5.
6.
Remove lock ring and retaining washer in front of
crankshaft gear.
Pull off crankshaft gear.
It
has two 1/4-20 UNC
tapped holes for attaching a gear pulling ring.
Use care not to damage teeth if the gear is to be
reused.
See
Figure 115.
Remove oil pan, pistons and connecting rods.
Remove bearing cap from center main bearing.
Remove rear bearing plate from crankcase.
Remove crankshaft through rear opening in
crankcase. Catch upper half of center main bear-
ing support as
it
slides
off
its mounting surface.
inspecfion:
Clean the crankshaft and blow out all oil
passages. Check journals for out-of-round, taper,
grooving or ridges. Pay particular attention to ridges
or grooves on either side of the oil hole areas. Unus-
ual conditions here often point to previous neglect of
oil changes.
If journal dimensions are not within limits, or the
journals are scored, regrind the crankshaft.
Crankshaft Grinding:
Crankshaft grinding requires a
trained, experienced operator working with precision
equipment. Procedures which may besatisfactoryfor
some spark-ignition engines may well be unsatisfac-
tory for diesel applications, resulting
in
expensive
f ai
I
ures.
Special procedures must be observed when rework-
ing diesel crankshafts.
In
addition to machining, the
crankshaft must be shot-peened and super-finished.
Failure to
shot-peen
the crankpin fillets is likely to
cause early failure. When the shaft is machined, fol-
low the directionsand dimensions given in Figure 116
to shot-peen each crankpin fillet.
THIS
AREATO
BE
MASKED
DURING
SHOT-
PEENIN6
OPERATION
I
FIGURE
116.
SHOT-PEENING THE CRANKSHAFT
1. Almen gauge reading 0.012-A
(0.305).
2.
Peen with 0.019 inch (0.482 rnm) .diameter cast
3. Peen for
30
seconds on each crankpin fillet.
4. Mask
off
connecting rod bearing areas.
Undersize bearings and connecting rods are availa-
bleto
reworktheshaftto0.010inch
(0.254rnm),0.020
inch (0.508 rnm), and
0.030
inch
(0.762
mrn) undersize.
steel shot.
Main Bearings:
Replace main bearings if clearances
are greater than limits or if the bearings are worn,
grooved, or broken.
Precision replacement inserts and thrust washers are
available for all main bearings.
Do
not ream the
bearings.
Align the oil holes and press the new bearings into the
front and rear housings. Insert the center bearing
when the crankshaft is reinstalled.
Rear
Oil
Seal;
The rear oil seal is in the rear bearing
plate. If damaged, drive
it
out from the inside of the
plate. Using the oil seal installing tool (Onan
No.
420-0250), install a newsealwith the rubber lip facing
outward (open side of seal inward). See Figure 117.
Drive the new seal flush
with
the rear surface of the
bearing plate. Leave the seal installer on during bear-
ing plate installation to protect the oil seal.
Installation:
After each installation step, check the
crankshaft to be sure
it
is not frozen into place.
1. Press front and rear main bearings into place,
then align bearing and bearing housing oil holes.
Do
not attempt to drivea bearing into a cold block
or
rear bearing plate.
2. Install thrust washers and locking pins.
3.
Oil bearing surfaces and install crankshaft from
rear of crankcase through rear bearing plate hole.
Redistribution or publication of this document,
by any means, is strictly prohibited.
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