OA-331 Rear Main Seal Replacement - Anybody interested?

[rflegal]

Hey guys, been around for a while and checking in but haven't posted in ages; been way too busy.

I have finally finished up the rebuild of the transmission in my M36 after the woodruff keys stripped out on 2nd/3rd.
That was a lot of work, but well worth it from a learning standpoint.
Lots of help from the folks and resources here and now I'm ready to put it back in.

Had the flywheel machined, new clutch, new throw out & pilot bearings; all good to go. Pilot was a bear to get out - used the grease method after the puller wouldn't get it.

Anyway - decided to replace the rear main seal too as the inside of the bellhousing was wet and the old clutch indicated some leakage. Thanks to this board, it hasn't been that daunting of a task. I really appreciate everyone's posts here. So before I went ahead and whipped through the install, I thought I check to see if anyone would be interested in me documenting the procedure? Thought I might give back a bit to the forum.

I have cross-referenced the new seal from the old WHITE # to several others but was able to find the National part as the quickest available. Bought two just in case I goofed one up.



485915H

As I said, bought two - it is a good replacement. I will have an extra carrier too, fully loaded then. Not sure why I would need it but these things are getting harder to find.

In changing the seal - Yes, you do need to drop the oil pan to replace the seal. Yes, it is a pain; but not really that big a deal. Mine was pretty much glued to the engine by the PO because they didn't have a proper gasket. It took a lot of effort to get it separated.

Yes, you should try to find a gasket set if you have one of these old OA-331s (in this case for the oil pan gasket). I found one set and never will use it but rather make new gaskets from fresh cork or gasket sheet using the army issue as a pattern. If you buy a cheap punch set you can knock what you need out pretty fast. I've picked up a couple extra head gaskets as well.

Anyway, I have already dropped the pan and removed the seal holder; was very happy to see how nice and tiddy my lower short block was.

I'm gonna try and put it all together this coming weekend. I will probably never need to do this again, but if folks are truly interested, I'll make the effort to document with some photos. Just didn't know if anyone was still playing with these old gassers anymore.

Let me know if anyone wants photos. Otherwise, I'll just get 'r done. Wish me luck.

 

[JasonS]

Nobody comes to this forum to read. Pictures are always fun.

 

[OD_Coyote]

I have an M47 gasser and would be interested in seeing the photos.

 

[rflegal]

OK - so I finally have everything prep'd, cleaned and ready so today I installed the seal and the flywheel. Still need to do the oilpan.

Anyone working on their gasser should try to find a copy of TM 9-8023-1 and the parts TM 9-2805-222-34P. The reprint of the 8023 that I have is still available on Ebay and is excellent; just search "TM 9 8023". It is not my listing.

This is the stuff from the TMs -

 

[rflegal]

And now the install. A few notes: there is an "oil slinger" on the rear of the crankshaft, looks like a big spring ring, like the ones you find inside of some lipped seals. The TM says it was added to engines after # 118193.

Also make sure you position the crankshaft to permit access to the five cap screws that fasten the lower half of the seal retainer from the crankcase side.

Also note, the 5 cap screws are two different size; two are longer. The longer ones install on each side near the oil pan rail. The shorter ones install on the lower, middle holes.

When installing the actual seal, a small hint; I used my press and pressed it in, but used the old seal as a spacer to press the seal the whole way in. If you notch it with a hacksaw, you can use the old seal as a space and be able to remove it easily. Don't just use the old seal as is - you'll struggle to get it back out.

So, here's your pics:

In the shop - had to make a new gasket too. The material is the thin, oil type paper, not cork. Use no RTV, shelac, etc. Just oil it for install.
Note new pilot bushing.

 

[rflegal]

Note the different size cap screws.



Oil slinger is in the pictures too.

The cap screws have a copper/bronze sealing washer under the cap. The TM says to pitch and replace but I didn't have replacements so I left as is and simply added some non-hardening gasketcinch under the head. These bolts weren't installed terribly tightly when I removed them, and I couldn't find and specs for torquing.

 

[rflegal]

Finally - out in the truck...
It was a perfect day, not too hot, not too cold, not too windy...

Already cleaned up the bellhousing... cleaned up the crank surface as well using a scotch bright.



Note the oil pan is off and the crank is protected with a bag and duct tape.

 

[rflegal]

Finally, all the parts in place. If you install right, this is what she should look like...



Had just enough time and daylight to install the flywheel. I couldn't find torque specs anywhere, so I check some of my truck manuals and settled on 100 ft-lbs. Anyone know any better?



Well - that's all for now. Gotta get the oil pan refurbed and installed.

Hope all this helps someone. I can't stress enough how useful the TMs are for this. Study 'em up.

 

[OD_Coyote]

Thanks for the info and pics rflegal!

 

[Nationwide 63s]

Thanks for the INFO!! I think I'll be heading down that same path soon! LOL!

 

[rflegal]

No worries - hope it helps - the seal number posted in #1 worked very well. I recommend it. - Bob