Small block w/ automatic rear main seal question

hey guys,

Can you replace an LA small block rear main seal with both the
engine and trans installed in the car..

If so, do I need any special tools, tips etc?

IF any one on here has done this job please chime in
Thanks

yes...Done it in a couple of pickup trucks last year.

no special tool..just need to push upper half of neoprene seal out...

lubed the new one and pushed it into upper half...

Not quite so easy if it's a rope seal.Get yourself one of those corkscrew type seal remover tools. Might even help if you carefully loosen the #4 main cap a bit.

I believe Lisle Tools has the seal removal tool.


https://www.ebay.com/i/282433611363?chn=ps

Have you made sure that the main seal is leaking and not something else?
I've seen more than one car have the rear main seal replaced several times when it wasn't leaking to start with
Does the flexplate or flywheel flange have oil slung out on the surface that faces forwards?
If not it is not the main seal leaking
The rear cam bearing plug or the rear oil galley plugs can leak and look a lot like a rear main seal leak
Good luck either way
I have loosen all five main caps with the engine and tranny in the car to replace the rear main seal on BB and early hemi motors, not sure if I have done that on a LA SB

I just replaced a rear main seal on a big block a month ago and this is what I learned. Most if not all of this applies to small blocks too.

1. You can change it with motor/trans in place. You will need to break loose the pitman arm & idler arm to lower the center/drag link enough to get the pan off. Leave the tie rods alone & you won't mess up your alignment.
2. Oil galley plugs & rear cam seal (looks like freeze plug) can leak, but that is very rare.
3. There are 2 types of seals, 1-piece rope seal and 2-piece seal. Rope seals better but is MUCH harder to install remove. You need a "Chinese finger lock" tool to install it and a screw-in tool to remove it. Loosening the #5 main bearing cap (or all of the main bearings) might help. If using a 2-piece seal, it is stiff, so you can slide the top half up/around the top of the crank without loosening any bearings. TRIPLE check which way the lip of a 2-piece seal goes on both halves...the lip faces the engine, not the trans like is "seems" (ask me how I know)
4. For either seal, lube well with assembly lube.
5. For a 2-piece seal, make sure to offset the two halves about 1/8" so the break between the two halves doesn't line up with the break in the rear seal cap.
6. Make SURE your cap is clean & free of debris.
7. Use a single drop of special Loctite seals (check online for which one) where the two halves of the seal butt up against each other.
8. Use about 2 drops of RTV on the rear main cap surface where it butts up against the block, no more.
9. Tighten the rear seal cap slowly and make sure it goes in even.
10. Almost forgot, lube the side seals of the rear seal cap too.
11. Buy the good silicone 2-piece main seal & side seals, not the Felpro ones.

Hppe most of this helps & good luck.... and MAKE SURE it's the main seal & not the back of a valve cover or something else leaking first. Hughes Engines site has some very helpful information too.

Hey guys, THANKS for all the responses! The parts book lists a 2 piece seal....Is there a particular brand that you used or recommend? I'm also thinking while I'm at it - upgrade from a stock oil pump to a high volume Melling oil pump...anyone done this/recommend it? thanks for all the feedback

If it was rope it wouldn't be leaking... My advice would be to pull it and install the rope. Do it right and it will never leak. The lip seals will.
Rope seals are two piece but they are a snug fit (hence the never leaking) and need to be trimmed to fit - so slipping one in is not as easy.

I use to work in several different service station near a Marine base back in the early 1960s when rope seals where stock OEM in all new Mopar motors, I saw more than one rear main seal leak back then
I've rebuilt motors and had to use the OEM style rope seals, once the new style rubber and later Neopreme came out and now the newest Viton seals sold today I haven't had a rear main seal leak in over twenty years, I have had the old side seals leak on BB Mopars years ago but not anymore
If the factory can make the stock rear main seals not leak then we should be able to get the same results, no matter which type or material used
The old technology and parts where invented years ago, they are not as good as the modern ones used today