Rear Main Seal

[chevmn]

Replacing the 2 piece rear main seal on a 72 402. Original seal. Pan is off, oil pump off, and rear main cap off. Any tricks to pushing the old seal out? According to most on Youtube, etc, it is a simple process, just push it out......not so easy for mine. I have ordered a Lisle 27000 Sneaky Pete Tool off amazon in case, but not positive this will help. Thoughts or voices of experience?

[PbFut]

Use the cap side old half or sacrifice a new seal to start a push on the old seal. Carefully grab the tip as it begins to protrude making sure not to touch any part of the crank bearing surface with any metal. Pull on the seal in an arching manner. It it should release pretty easily.

[RustyPile]

Originally Posted by chevmn

Replacing the 2 piece rear main seal on a 72 402. Original seal. Pan is off, oil pump off, and rear main cap off. Any tricks to pushing the old seal out? According to most on Youtube, etc, it is a simple process, just push it out......not so easy for mine. I have ordered a Lisle 27000 Sneaky Pete Tool off amazon in case, but not positive this will help. Thoughts or voices of experience?

That Sneaky Pete tool is for the old rope seal of the 50s - 60s.. Not for the modern 2-piece neoprene seal.. Loosen (but don't remove) all the other main cap bolts except #1. About 1/8" is all that's needed. Use a small brass punch to get the old seal started moving. Once the upper half is in place, re-torque the main cap bolts previously loosened. Install the lower seal half. Don't use any sealant anywhere on the seal pieces. Put a very small "dot" of sealant on the block in the rear main cap recessed "seat" area between the upper seal half and the end of the pan gasket. Install and torque the rear main cap. This procedure is referenced in the Engine (section 6) section of the Factory Service Manual.

[chevmn]

Originally Posted by RustyPile

That Sneaky Pete tool is for the old rope seal of the 50s - 60s.. Not for the modern 2-piece neoprene seal.. Loosen (but don't remove) all the other main cap bolts except #1. About 1/8" is all that's needed. Use a small brass punch to get the old seal started moving. Once the upper half is in place, re-torque the main cap bolts previously loosened. Install the lower seal half. Don't use any sealant anywhere on the seal pieces. Put a very small "dot" of sealant on the block in the rear main cap recessed "seat" area between the upper seal half and the end of the pan gasket. Install and torque the rear main cap. This procedure is referenced in the Engine (section 6) section of the Factory Service Manual.

I will try loosening all the main caps, except the front. Every other procedure I have seen does not mention this, only remove the rear main. Makes perfect sense to allow the crank room for seal to slide out more easily. I actually realized I have the 72 factory service manual, but the one I have makes no mention of loosening anything but the rear cap. May have been added in later versions.

[kwmech]

Carefully with a small round punch find the center of the seal which is a piece of metal and lightly tap it to crack it loose. I said carefully

[57taskforce]

Originally Posted by kwmech

Carefully with a small round punch find the center of the seal which is a piece of metal and lightly tap it to crack it loose. I said carefully

This is how I do them. I’ve never loosened any main bolts ever other than the rear most cap.

[chevmn]

Had a delay so no progress in last few days, but pushing on the metal portion of the seal, and tapping with a small punch has been fruitless so far, so next step is loosening all the main caps. I believe the issue is the fact this seal has been in there since late 1971, and then it had sat in a field since somewhere around 1983. I have obviously had it running as of the last year while I work on the truck, but started noticing the rear main leaking, so I decided to replace. Most of the gaskets, and other seals had already been replaced, along with timing set. Engine has roughly 63,000 miles. Pretty sure loosening the rest of the main caps, and maybe a little downward pressure on the crank should allow it to break free. No plans to rebuild as I do not see any need.

[kwmech]

Originally Posted by 57taskforce

This is how I do them. I’ve never loosened any main bolts ever other than the rear most cap.

Same here. Back in the days when i worked at a dealer, I did quite a few of these. Back then, sometimes the factory (or whoever assembled) would use that old style head gasket sealer brown paste stuff on the backside of the seal that was against the block. It almost made it impossible to get the seal out. After a few of these, we found that the factory had problems with the new style oil pans when they stamped them out and it wasn't a main seal problem at all.

[LS short box]

When we did the install of the new seal we always put some engine oil on the lip of seal prior to installing to prevent any tearing of the seal on start up.

[72SB]

I use a hard nylon drift punch vs anything metal to get it started. Loosening the other main caps and tug the crank down slightly as even just loosening the main caps, the pistons will hold it up so just give it a little tug from the rear.

[chevmn]

All done and pan is back on. Not an easy task, mainly due to the harding of the old seal from over 50 years. I think loosening all the main caps, then finding a tool that would allow tapping (briskly) yet not damage the sealing surface of the crank finally did the trick. Sure glad I was not pressed for time, as I went at it off and on for days, and it was best to not persist, and lose patience, and do more harm. Hopefully I do not have to do another, but not betting on it, but I am in my 60's and this was my first. Thanks to all who offered suggestions.