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Old 03-26-2011, 01:14 PM
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replacing rear main seal

how hard is it to replace a rear main seal on a 87 k5 blazer, 350 small block with four wheel drive and do i have to drop the transmission?

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Old 03-26-2011, 01:28 PM
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how to replace rear main seal on 350 small block

i have a 87 k5 blazer with 350 and four wheel drive and the rear main seal is leaking very bad and i need to change it, does anyone have any tips on how to do it?
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Old 03-26-2011, 02:25 PM
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Hi
This is coped from the link
Rich
rear main seal

Pull the pan off and take the oil pump off of the rear main cap. Watch out for the oil pump drive shaft. I put the pump in the pan for safe keeping.

Now take the two bolts out of the rear main cap and remove the cap. Taking the old seal out of the cap side is a snap, it is the engine side that gives people head-aches.

If the old seal is a rope seal then you will need to screw in a very thin and long eye bolt for wood. Then grab the eye bolt with a screwdriver through the eye and as you pull the seal have a friend rotate the crankshaft in the same direction. It may want to fight you but just remember it is just rope so you will win the battle.

If the seal is one of the new neoprene seals do the same steps but just look out for the metal in the seal and you will get this one out too.

Replace the old seal with the newer style neoprene style they are much easier to install than the rope. Be sure the lip faces toward the engine so it will not leak.

When I replace the main bearing cap I spray the mating surfaces with some 3M High Tac spray. Then re-torque the bolts to 80 pounds feet. Install the oil pump making sure the oil drive lings up with the bottom of the distributor. Then tighten that bolt to 65 pounds feet of torque I think. Check these specs to be sure I am correct, it has been a long time you know.

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Old 10-13-2007, 01:11 AM
artsman artsman is offline
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Quote:
Originally Posted by karl1
i want to replace the 2 PC rear main seal in my 350 without removing the crank. how do i do this? what kind of seal works best? thanks

You did say if the engine is in the car. If it is and the cross member is in the way of dropping the pan, you will need to remove the threw bolts from the motor mounts, the trans mount bolt and jack up the engine about 3-1/2 inches using a piece of 2X6 or other block of wood between the jack and pan, after raising the engine, put the threw bolts back in the mounts and it will hold the engine up.
You will probably need to remove the fan or shroud. Rotate the damper so the timing mark is at the bottom, this will allow the pan to clear the crank. Remove starter, pan bolts, oil pump and rear main cap. The top half of the seal can be removed by tapping the end of it with a soft punch and grabbing the other end with pliers. The new seal should come with a thin piece of plastic to insert part way into the top half of the seal recess so the new seal can slide past it to avoid damaging it on the sharp metal edge. There is a flat spot on the cap next to the seal that requires a thin amount of sealer. Oil the new seal and install it so the ends don't line up with the main cap split, about 1/4 inch should work. Don't know if one brand of seal is better than the other. I would recommend a Felpro one-piece pan gasket. You really should get a shop or repair manual of some kind that covers this job. Torque spec for the main cap is 70-85 ft lbs and 60-70 ft lbs for the oil pump.

Last edited by richard stewart 3rd; 03-26-2011 at 02:38 PM.
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Old 03-26-2011, 02:42 PM
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jam yer hand down the back of the engine before you tear into it.

its verry common to have leaks from the back of the intake and oil presure switch that can fool you into dropping the oil pan
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Old 03-26-2011, 03:17 PM
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yes. you will have to remove transfer case and transmission to get to the rear main seal for replacement.
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Old 03-26-2011, 03:22 PM
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1987 350 is a one piece seal. You will have to pull the transmission and flex plate/flywheel. Good Luck.
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Old 03-26-2011, 03:24 PM
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Quote:
Originally Posted by mud bros
jam yer hand down the back of the engine before you tear into it.

its verry common to have leaks from the back of the intake and oil presure switch that can fool you into dropping the oil pan
X2 on this. it is much more common for the intake, sender or even valve covers to leak at the back.
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