Section XII. CRANKSHAFT AND MAIN BEARINGS
7-25. General. The crankshaft is a machined forging
remove the main bearing caps from the
with surface-hardened bearing journals. The shaft has
cylinder block. Be careful not to score or
passages drilled to carry oil, under pressure, to the
mar the crankshaft journals.
connecting rod bearings. Normally, it is not necessary to
remove the crankshaft gear from the crankshaft. The
use of five main bearings permits a main bearing to be
placed on each side of each connecting rod bearing.
This construction helps to eliminate vibration at high
speeds. The main bearings are removable, precision,
shell-type bearings. The upper shell of each bearing is
not interchangeable with the lower shell. No shims are
These precision-type shells are completely
finished before being put in place and no line reaming or
scraping is required.
7-26. Crankshaft and Main Bearings.
a. Removal and Disassembly.
(1) Remove the engine from the unit (para
(2) Remove the fan and drive belt (figure
(3) Remove the oil pan and seal adapters
(4) Remove the fan drive pulley, gear housing
(5) Remove the flywheel and bellhousing
(6) Invert the engine to facilitate removal of
main bearing caps and crankshaft.
and main bearing caps (3, 4, 5, 6).
Remove the main bearing caps and the
lower main bearings (7,8), one cylinder at
a time. Keep each bearing matched with
its bearing cap. It may be necessary to
Figure 7-60. Crankshaft and main bearings,
use a small pry bar to
removal and installation
Lower main bearing half
1. Cap bolt (8)
Center main bearing
2. Center cap bolt (4)
Upper main bearing half
3. Front main bearing cap
4. Intermediate main bearing cap (2)
5. Rear main bearing cap
6. Center main bearing cap