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.
  4.  
  5. Remove the timing chain.
  6.  
  7. Remove the flywheel.
  8.  
  9. Unbolt and remove the main and connecting rod bearing caps. Keep them in order.
  10.  
  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.
  14.  

INSPECTION



See Figures 1, 2, 3 and 4

Click image to see an enlarged view

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.
  2.  
  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.
  4.  
  5. Clean all oil passages in the block (and crankshaft if it is being reused).
  6.  

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.
  2.  
  3. Place a piece of plastic gauging material in the center of the bearing.
  4.  
  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.
  6.  
  7. Install the bearing cap and bearing. Place engine oil on the cap bolts and install. Torque the bolts to specification.
  8.  
  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.
  10.  

INSTALLATION



See Figures 5, 6, 7 and 8

Click image to see an enlarged view

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.
  2.  
  3. Install the lower bearing halves in the caps.
  4.  
  5. Use Plastigage® to check bearing fit.
  6.  
  7. When the bearings are properly fitted, install and torque the bearing caps.
  8.  
  9. Check crankshaft end-play to determine the need for thrust washers.
  10.  
  11. While you're at it, it's a good idea to replace the rear main seal at this time.
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  13. Install sufficient oil pan bolts in the block to align with the connecting rod bolts. Use rubber bands between the bolts to position the connecting rods as required. Connecting rod position can be adjusted by increasing the tension on the rubber bands with additional turns around the pan bolts or thread protectors.
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  15. Position the upper half of main bearings in the block and lubricate them with engine oil.
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  17. Position crankshaft keyway in the same position as removed and lower it into block. The connecting rods will follow the crank pins into the correct position as the crankshaft is lowered.
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  19. Lubricate the thrust flanges with clean engine oil or engine rebuilding oil. Install caps with the lower half of the bearings lubricated with engine oil. Lubricate the cap bolts with engine oil and install, but do not tighten.
  20.  
  21. With a block of wood, bump the shaft in each direction to align the thrust flanges of the main bearing. After bumping the shaft in each direction, wedge the shaft to the front and hold it while torquing the thrust bearing cap bolts.
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In order to prevent the possibility of cylinder block and/or main bearing cap damage, the main bearing caps are to be tapped into their cylinder block cavity using a wood or rubber mallet before the bolts are installed. Do not use attaching bolts to pull the main bearing caps into their seats. Failure to observe this information may damage the cylinder block or a bearing cap.

  1. Torque all main bearing caps to specification. Check crankshaft end-play, using a flat feeler gauge.
  2.  
  3. Remove the connecting rod bolt thread protectors and lubricate the connecting rod bearings with engine oil.
  4.  
  5. Install the connecting rod bearing caps in their original position. Torque the nuts to specification.
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  7. Install all parts in reverse order of removal. See related procedures in this chapter for component installation.
  8.  

 
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