Torsional Damper; Crankshaft And Bearings - Chevrolet 1988 Light Duty Truck Repair Manual

6A4-22 4.8 LITER L6
D isassem b le (F ig u re 4)
1. Bolts (55).
2. W ater outlet (54).
3. Therm ostat (52).
4. Gasket (53).
In sp ect (F ig u re 4)
W ater outlet (54) and housing (50) for cracks or
damage.
*
A s se m b le (F ig u re 4)
1. Therm ostat (52).
2. Gasket (53).
3. Water outlet (54).
4. Bolts (55).
&
T ig h ten
Bolts (55) to 40 N m (30 ft. lbs.).

TORSIONAL DAMPER

I?
In sp ect
— Torsional dam per w eight for looseness or signs of
shifting on the hub. Replace as needed.
— A rea of the to rsio n a l d a m p e r hub sh a ft w hich
contacts the front crankshaft seal for roughness or
nicks. Replace the dam per if this condition exists.

CRANKSHAFT AND BEARINGS

CLEANING AND INSPECTION
1 3 1
C lean
Crankshaft with solvent.
— Do not scratch the bearing journals.
— Blow all sludge from the oil passages with
com pressed air.
Main bearing inserts. W ipe free of oil with a soft
cloth.
I?
In sp ect
C rankshaft for cracks. Use the m agnaflux method, if
available.
C ra n k p in s , m a in b e a rin g jo u rn a ls and th ru s t
surfaces for scoring, nicks, or dam age caused by
lack of lubrication.
Main bearing inserts for scoring or other damage.
In g eneral, th e low er in se rts (except the #1
bearing) shows a greater wear and the most distress
from fatigue. If, upon inspection, the lower insert is
suitable for use, it can be assumed that the upper
insert is also satisfactory. If the lower insert shows
evidence of wear or damage, both upper and lower
inserts must be replaced.
C rankshaft gear for chipped or dam aged teeth.
M easu re (F ig u re s 42 and 43)
— Main bearing and connecting rod journal diameters
(figure 42). Com pare with " S pecifications." Grind or
replace the crankshaft if necessary.
Figure 42 — Measuring the Crankshaft Journals
— Main bearing and connecting rod journals for taper
and out of round (figure 42). If the journals are
tapered or out of round more than 0.001-inch, grind
or replace the crankshaft.
— Crankshaft runout (figure 43).
• M ount the crankshaft in V-blocks or between
centers.
• Use a dial indicator as shown.
• If the main bearing journals are misaligned,
the crankshaft is bent and must be replaced
along with the main bearings.
CRANKSHAFT GRINDING
A " tu f ft r id in g " h a rd e n in g p ro c e s s is a p p lie d to
crankshaft jo u rna ls used in engines covered by this
manual. The crankshaft should not be reground unless it
can be tufftrided after grinding.
Figure 43 — Checking Crankshaft Runout
B-00549
B-02792