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Discussion Starter #1
I've got a late 60's/early 70's M21 that I've been running for a couple of years and it has always leaked. I've just pulled it out and it seems to leak thru the front bearing. I don't understand what keeps this from leaking. The round flange with the nose cone (bearing retainer) has a gasket and 4 blots. It's has a hole at the base of the nose cone, as I suppose a drain. My bellhousing was full of lube.

I see no way for a seal, and the book doesn't show one. Do I have it too full?
How do I keep lube out of my Bellhousing and off the garage floor?

THANKS
 

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How full are you filling it?.....It should be filled to the fill hole on the side, no more.

There must be a seal on the input shaft somewhere as well as that gasket.
 

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Discussion Starter #3
M21 leaks

I think that it would be hard to fill past the fill hole, but I may have tried to squeeze a little extra in. I would think that little bit has leaked out by now. I see no place to install a seal and see nothing in any of the publications that I have. It sure is leaking. I appreciate any thoughts you have!
 

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bad drive line angle. The tranny should be tipped back a few degrees. What type of vehicle is this in. it could be overfilled or have the wrong type of fluid in it. Overfilling would be difficult
 

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Discussion Starter #5
M21 leaks

Thanks for the response!
It's in a 69 Firebird and the car does have some rake to it. I believe that I have 80w90 gear lube. Can I run something else that would help?
 

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leak

My guess would be that the input nut is installed backwards... Most muncies that leak oil out the retainer are caused by the nut being installed wrong. The face of the nut that is machined on a radius needs to face the bearing retainer. This is a oil slinger arrangement and also how the transmission is vented.There is NO seal there. If you don't have the special thin wrench to install the nut you will need to buy one.

Also inspect the face of the retainer where the nut is located for ware. Many times this surface looks like a plowed field. Thats no good. It,along with the nut need to be smooth...

Also, the bolt holes are thru into the case and need a bit of sealer on them so the oil don't weep out the threads...

Are you positive the oil is coming from the retainer???? A more common problem with the Muncies is the counter shaft working in the bore of the case and oblonging(sp?) it...


if everything is installed in the stock location the RAKE is not the problem

Keith
 

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Discussion Starter #7
M21 leaks

Thanks.... this is great information. I'll first check the nut. If it's wrong, where can I buy the wrench and how tight do I put it back.

When you talk about the face of the retainer are you speak to the mating surface where the gasket lays? If so, that is fine.

When I turn the input shaft counter-clockwise while looking at it from the engine side (with the retainer removed), lube come from around the bearing and out the two lower retainer holes. I figured out last night that those retainer bolt holes needed sealant. The counter shaft seems to remain dry.
 

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Muncie

If you look at the retainer side that mates with the transmission there is a finish diameter the same size as the outside diameter of the slinger nut. It is down inside the bearing retainer.. I think it's the second step... I don't have one in front of me to be sure...But you will see it easy...


The best place for you to get the wrench would be on e-bay... I sell them also if that does not work out for you..Pm me if you can't find one...

Resist the temptation to use a pipe wrench or other cave man tool to tighten this nut up... Marking that nut will cause it to leak oil out the retainer..

Not sure i have ever seen a torque value for the input not but you can't make them to tight....I also clean all the oil from the input threads and the nut threads and use some blue loctite on them.... from the factory they would punch the nut at the oil hole in the input to stake it in place... I personally don't care for that, nothing wrong if you choose to do it but i don't...I never had any issues with the nut coming loose with the blue loctite...


Keith
 

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The only muncies I saw leak out the cluster shaft hole were early ones with a 7/8 inch cluster shaft. Late 1 inch shaft boxes - even with Liberty gears seemed to seal alright.
I too have seen many input nuts butchered. On the nose cone bolts try Loctite #515 if it's still available - it's a great thread sealant that doesn't damage threads.
 

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IanRiordan said:
The only muncies I saw leak out the cluster shaft hole were early ones with a 7/8 inch cluster shaft. Late 1 inch shaft boxes - even with Liberty gears seemed to seal alright.
I too have seen many input nuts butchered. On the nose cone bolts try Loctite #515 if it's still available - it's a great thread sealant that doesn't damage threads.

Whats funny in my shop,,, I see the exact opposite...I would say that i get (10) 1" pin cases with the bore/bores over sized for every (1) 7/8" pin case that is big....


Keith
 

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It'd be cool to machine a groove on the cluster pin for an o'ring[near the edge of the case]

I'm sure somebody is doing it.

May not work though,problems with needles[clearance]

But a groove in the case itself,for an o'ring,I bet that would work!
 

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bore

What i do is set them up on my mill and bore the case out for a stepped bushing. I then make a bushing out of steel and press it into the case and finish bore it inline..... I will usually make it about a .0005" fit with the pin. Once i do that fix they never leak again....

The new aftermarket cases use a freeze plug in the front pin to eliminate this issue.....



Keith
 

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leak

I don't think the "O" would be the best fix. I am sure it would work to fix the leak, but the reason for the leak is because the bore that supports the cluster pin is worn out.... You really need to restore the bore to correct that problem...


Keith
 

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Thanks,machine shops are having a rough go of it,some in this area are closing,a good deal on a mill may come along. Thanks again for your input! Dana
 

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Hey K-star, maybe the bulk of the 7/8 (early) boxes you see came out of light pre 66 small block cars and the 1 inch shaft ones are mostly out of BB Chevelles, Goats etc. Here Muncies were rare and whilst there was 1 known ZL1 4SPD Camaro to come here new most muncies arrived in small block cars destined for circuit racing. The only local car to have a factory muncie (called an m22 by Holden but actually a late fine spline m20) was the 1971/74 Holden Monaro GTS350 - 3400lb/275hp 350.
If a case has elongated holes here it gets bored and bushed.
Briscoe, keep that lathe tool away from a case hardened shaft. you'll create a stress riser and break it assuming you were smart enough to wear safety goggles and still have eyes to assemble the 4 spd. The welsch plug sounds like a good idea - I always thought that 1/8 inch off the front of the shaft and a plug like an sbc cam plug would work.

My first muncie was a 10 spline stud and nut M22, then I ran a sucession of m20s which allowed me to remove my ear plugs.
 

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Hey Ian,thanks for the words of caution,sounds like you may have had a bad experince,in this area mate. Will heed your warning,what k-star is doing is a neat idea anyway. And by the way,glad to see you were smart enough to wear ear plugs.
 

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muncie

Ian, I too have considered the approach of shorting the counter shaft and installing a flat plug in the case.. But i keep thinking that when you do it you will be removing more area of the shaft to case contact.... I know 1/8" is not alot but since it's a problem now making it less would only add to the issues..IMO...

I feel i would rather have a small leak then take strength away from the pin support....


Keith
 

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How about 4 tapped holes with a flat plate cover, it would need a small dia drain back hole into the case - say 45 degrees at 6 o'clock.
Further, like crankshafts in some early engines you could cut a 5 thou coarse thread- an 'Archimede's screw' in the cluster shaft. Ok the shaft doesn't turn but the rollers should drive the oil rearward into the case. Ol' Arc was a switched on cat for an ancient Greek, his screw still lifts millions of tons of grain and water every year.
Dunno if you folks get world news but the bushfires are pretty bad here, lots of smoke - visibility down to a 1/4 mile at times.
 
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