REMOVAL & INSTALLATION
1987-90 7.4L Engines
See Figures 1 through 5
- Remove the oil pan, oil pump and rear main bearing cap.
- Remove the oil seal from the bearing cap by prying it out with a suitable tool.
- Remove the upper half of the seal with a small punch. Drive it around far enough to be gripped with pliers.
- Clean the crankshaft and bearing cap.
- Coat the lips and bead of the seal with light engine oil, keeping oil from the ends of the seal.
- Position the fabricated tool between the crankshaft and seal seat.
- Position the seal between the crankshaft and tip of the tool so that the seal bead contacts the tip of the tool. The oil seal lip should face forward.
- Roll the seal around the crankshaft using the tool to protect the seal bead from the sharp corners of the crankcase.
- The installation tool should be left installed until the seal is properly positioned with both ends flush with the block.
- Remove the tool.
- Install the other half of the seal in the bearing cap using the tool in the same manner as before. Light thumb pressure should install the seal.
- Install the bearing cap with sealant applied to the mating areas of the cap and block. Keep sealant from the ends of the seal.
- Tighten the main bearing cap retaining bolts to 10 ft. lbs. (14 Nm). Tap the end of the crankshaft first rearward, then forward with a lead hammer. This will line up the rear main bearing and the crankshaft thrust surfaces. Tighten the main bearing cap 110 ft. lbs. (150 Nm).
- Install the oil pump.
- Install the oil pan.
See Figures 6, 7 and 8
Special tool J-35621 (or J-38841), or its equivalent seal installer, will be necessary for this job.
- Remove the transmission.
- With manual transmission, remove the clutch.
- Remove the flywheel or flexplate.
- Insert a small prying tool in the notches provided in the seal retainer and pry out the old seal. Be VERY CAREFUL to avoid nicking or scratching the sealing surfaces of the crankshaft.
- Coat the inner and outer diameters of the new seal with clean engine oil.
- Using seal tool J-35621, or equivalent, position the seal on the tool.
- Thread the attaching screws into the holes in the crankshaft end and tighten them securely with a screwdriver.
- Turn the installer handle until it bottoms.
- Remove the tool.
- Install the flywheel/flexplate, clutch and transmission.
See Figures 9, 10 and 11
The crankshaft need not be removed to replace the rear main bearing upper oil seal. The lower seal is installed in the bearing cap.
Engines are originally equipped with a rope-type seal. This should be replaced with the lip-type seal available as a service replacement.
- Drain the crankcase oil and remove the oil pan and rear main bearing cap.
- Using a special main seal tool or a tool that can be made from a dowel (see illustration), drive the upper seal into its groove on each side until it is tightly packed. This is usually 1 / 4 - 3 / 4 in. (6-19mm).
- Measure the amount the seal was driven up on one side. Add 1 / 16 in. (2mm) and cut another length from the old seal. Use the main bearing cap as a holding fixture when cutting the seal as illustrated. Carefully trim protruding seal.
- Work these two pieces of seal up into the cylinder block on each side with two nailsets or small screwdrivers. Using the packing tool again, pack these pieces into the block, then trim the flush with a razor blade or hobby knife as shown. Do not scratch the bearing surface with the razor.
It may help to use a bit of oil on the short pieces of the rope seal when packing it into the block.
- Apply Loctite® # 496 sealer or equivalent to the rear main bearing cap and install the rope seal. Cut the ends of the seal flush with the cap.
- Check to see if the rear main cap with the new seal will seat properly on the block. Place a piece of Plastigage® on the rear main journal, install the cap and tighten to 70 ft. lbs. (94 Nm). Remove the cap and check the Plastigage® against specifications. If out of specs, recheck the end of the seal for fraying that may be preventing the cap from seating properly.
- Make sure all traces of Plastigage® are removed from the crankshaft journal. Apply a thin film of sealer (GM part # 1052357 or equivalent) to the bearing cap. Keep the sealant off of both the seal and the bearing.
- Just before assembly, apply a light coat of clean engine oil on the crankshaft surface that will contact the seal.
- Install the bearing cap and tighten to specification.
- Install the oil pump and oil pan.
See Figure 12
- Disconnect the negative battery cable. Drain the oil.
- Remove the oil pan and oil pump.
- Loosen the bolts and remove the rear main bearing cap. Pull out the old rope seal.
- Clean the upper and lower seal grooves. Clean the main bearing cap and block mating surfaces and then check the bearing clearance.
- Coat the inner side of the seal halves where they contact the crankshaft and slide them into position.
- Roll one seal half into the cylinder block groove until 1 / 2 in. (13mm) of the seal's end is protruding from the block.
- Insert the other half into the opposite side of the groove. The ends of the seals (where they touch) should now be at either the 4 and 10 o'clock or the 8 and 2 o'clock positions. This is the only way you will be able to align the main bearing cap and seal lips properly!
- Coat the seal groove in the bearing cap lightly with adhesive. Apply a thin film of anaerobic sealant to the cap (stay away from the oil hole!!), coat the bolts with oil and tap them into position. Tighten all bolts to specification, loosen and then re-tighten.
- Install the oil pan and pump. Fill the engine with oil and connect the battery cable.