Home » Duramax LLY » Duramax LLY – CRANKSHAFT BEARING – Replacement In-Vehicle

Duramax LLY – CRANKSHAFT BEARING – Replacement In-Vehicle

The crankshaft main and rod bearings can be replaced without having to remove and completely disassemble the engine.
The rod bearings only require that the piston be at or near bottom dead center for access. The main bearings are rotated out of the bearing saddles with a 1/8 in. cotter pin or with equivalent. Procedure is as follows:
1. Disconnect battery cables at batteries.
2. Remove skid plate/underbody protector, if equipped.
3. Drain engine oil from oil pan.
4. Remove oil pan.
5. Remove oil pump.
6. Replace rod bearings as follows:
a. Rotate crankshaft in counterclockwise direction until connecting rod cap attaching nuts are accessible.
b. Remove rod cap nuts. Note position of rod cap for installation reference.
c. Remove rod cap and lower half of bearing. Then push piston upward slightly and remove upper half of bearing.

NOTE: Connecting rod bearings are select fit parts. Record the color code markings on each bearing half for parts ordering and installation reference. Also note if cap was marked with ‘OS’ code which indicates oversize bearings are required.
d. Clean connecting rod and crankshaft bearing surfaces and dry with lint free shop towels.
e. Install bearing halves in rod cap and in rod. Be sure bearing locating tangs are seated in cap and rod notches.
f. Check bearing clearance with plastigauge. Clearance should be 0.0017-0.0039 in. (0.045-0.100 mm). Then remove rod cap, clean plastigauge off surfaces, lubricate crankshaft and bearing surfaces with engine oil and reinstall rod cap. Tighten new cap nuts to 44-52 lb-ft (60-71 N.m) torque.
lb-ft (60-71 N.m) torque.

7. Replace main bearings as follows:
a. Loosen bearing cap bolts at adjacent bearings.
b. Remove bearing cap bolts at first bearing to be replaced, and remove cap and bearing lower half (mark cap for reference before removal).
c. Insert tool J-8080 into oil hole in crankshaft bearing journal. Position ‘T’-end of tool against bearing upper half. Rotate crankshaft counterclockwise until tool pushes upper half of main bearing out of bearing saddle in block (Figure 2-48).
d. Clean main cap, crankshaft journal, and bearing saddle in block with solvent. Refer to overhaul section for bearing specifications and select fitting.
e. Start plain end of new upper bearing half into place by hand. Then push bearing into position with tool J8080. Be sure bearing tang is seated in notch in bearing saddle of block (Figure 2-48).
f. Check bearing clearance with plastigauge. Clearance should be 0.0017-0.003 in. (0.045-0.083 mm) for bearings one through four and 0.002-0.0036 in. (0.055-0.093 mm). Remove main cap, clean plastigauge off surfaces, lubricate bearing halves and crank journal with engine oil. Tighten new main bearing cap bolts as follows:
– inner bolts to 111 lb-ft (150 N.m)
– outer bolts to 100 lb-ft (136 N.m)

8. Install oil pump.

9. Apply RTV-type sealer to oil pan sealing surfaces and install pan. Tighten all but two rear pan bolts to 89 lb-in. (10 N.m) torque. Tighten two rear pan bolts to 17 lb-ft (23 N.m) torque.

10. Install new oil filter and refill with engine oil. Use SAE 10W-30 for temperatures under 40¡F and 15W-40 for temperatures above that figure.

11. Connect battery cable and reinstall skid plate.

12. Test run. Test for leaks.



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