Jeep Wagoneer/Commando/Cherokee 1957-1983 Repair Information

Crankshaft and Main Bearings

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REMOVAL & INSTALLATION All Engines



This procedure is best done with the engine out of the vehicle and mounted in a work stand.

  1. Remove the oil pan.
  2.  
  3. Remove the oil pump.
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  5. Remove the timing chain.
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  7. Remove the flywheel.
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  9. Unbolt and remove the main and connecting rod bearing caps. Keep them in order.
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  11. Lift the crankshaft out of the block.
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  13. If the bearings are being replaced, note the positions of the oil holes for installation, and remove the bearing halves from the caps and block saddles.
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INSPECTION



See Figures 1, 2, 3 and 4

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Fig. Fig. 1: A dial gauge may be used to check crankshaft end-play



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Fig. Fig. 2: Carefully pry the shaft back and forth while reading the dial gauge for play



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Fig. Fig. 3: A dial gauge may also be used to check crankshaft run-out



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Fig. Fig. 4: Turn the crankshaft slowly by hand while checking the gauge

  1. Check the crankshaft for wear or damage to the bearing surfaces of the journals. Crankshafts that are damaged can be reconditioned by a professional machine shop.
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  3. Using a dial indicator, check the crankshaft journal runout. Measure the crankshaft journals with a micrometer to determine the correct size rod and main bearings to be used. Whenever a new or reconditioned crankshaft is installed, new connecting rod bearings and main bearings should be installed.
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  5. Clean all oil passages in the block (and crankshaft if it is being reused).
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A new rear main seal should be installed any time the crankshaft is removed or replaced.

  1. Wipe the oil from the crankshaft journal and the outer and inner surfaces of the bearing shell.
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  3. Place a piece of plastic gauging material in the center of the bearing.
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  5. Use a floor jack or other means to hold the crankshaft against the upper bearing shell. This is necessary to obtain accurate clearance readings when using plastic gauging material.
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  7. Install the bearing cap and bearing. Place engine oil on the cap bolts and install. Torque the bolts to specification.
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  9. Remove the bearing cap and determine the bearing clearance by comparing the width of the flattened plastic gauging material at its widest point with the graduations on the gauging material container. The number within the graduation on the envelope indicates the clearance in millimeters or thousandths of an inch. If the clearance is greater than allowed, replace both bearing shells as a set. Recheck the clearance after replacing the shells.
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INSTALLATION



See Figures 5, 6, 7 and 8

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Fig. Fig. 5: Illustration of the steps used to align the thrust bearing before tightening



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Fig. Fig. 6: Checking rod side clearance with a flat feeler gauge. Use a small prytool to spread the rods



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Fig. Fig. 7: Checking the crankshaft end-play using a dial indicator



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Fig. Fig. 8: Checking the crankshaft end-play using a feeler gauge

Main bearing clearances must be corrected by the use of selective upper and lower shells. Under no circumstances should the use of shims behind the shells to compensate for wear be attempted.

  1. Install new bearing upper halves in the block. If the crankshaft has been turned to resurface the journals, undersized bearing must be used to compensate. Lay the crankshaft in the block.
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  3. Install the lower bearing halves in the caps.
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  5. Use Plastigage® to check bearing fit. <