muncie transmission drain/fill plug replacement
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Team Owner
Joined: Jul 1999
Posts: 26,545
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From: Huntersville NC
muncie transmission drain/fill plug replacement
I have really mangled my drain plug trying to get it off. (I got it off a year ago but have been unsuccessful this time!) When I finally get it off I would like to get a replacement. Are these things available as a GM part #? Any ideas where to get one? Are they mostly interchangeable? I have a 68 with M20 tans. MJ
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Joined: Jan 2001
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From: South Central Louisiana
St. Jude Contributor
Re: muncie transmission drain/fill plug replacement (MNJack)
It may even be a standard 1/2" pipe plug, but then you will want a magnet in it. I am sure any parts house will have them. If not, there is a website that specializes in muncie transmission.
Drifting
Joined: Feb 1999
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From: Fremont, CA, USA
Re: muncie transmission drain/fill plug replacement (MNJack)
MJ-------
The GM replacement transmission drain plug is GM #3968034. This is a 1/2" NPT magnetic-type plug. At the moment I could not tell you if the head design is the same as original, though. It currently GM lists for $5.00.
The GM replacement transmission drain plug is GM #3968034. This is a 1/2" NPT magnetic-type plug. At the moment I could not tell you if the head design is the same as original, though. It currently GM lists for $5.00.
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Joined: Jul 1999
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From: Huntersville NC
Re: muncie transmission drain/fill plug replacement (Joe Lucia)
714544spd, thanks - looks like you hit it, but you gotta love those GM part numbers!! 
Joe, as always, thank you! So the standard GM part is magnetic? Any idea when they started magnetizing them? Were they magnetic in the 60s? Hmmmm... maybe that's why I cant get mine off - the magnet is holding it in place.... MJ :smash:
[Modified by MNJack, 11:17 AM 8/7/2001]
Joe, as always, thank you! So the standard GM part is magnetic? Any idea when they started magnetizing them? Were they magnetic in the 60s? Hmmmm... maybe that's why I cant get mine off - the magnet is holding it in place.... MJ :smash: [Modified by MNJack, 11:17 AM 8/7/2001]
Drifting
Joined: Feb 1999
Posts: 1,351
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From: Fremont, CA, USA
Re: muncie transmission drain/fill plug replacement (MNJack)
Magnetic transmission plugs were rarely used before 1970, although some earlier M-22 may have used them. Beginning in about 1970, the trans drain plug started appearing on all Muncie cases with the '661' casting number. The magnetic drain plug was then used. I think that it may have replaced the magnet that was cemented to the bottom of the earlier Muncie main cases. Yes, that's right, many pre-1971 Muncie main cases (and maybe even some 71+) have a magnet GLUED to the inside, front portion of the main case.
A drain plug magnet (even if your car is equipped with a magnetic drain plug) is not responsible for your difficulty in removing the plug. These plugs are steel or cast iron and the case is aluminum. Therefore, for some reason or another, the interface is subject to dissimilar metal (galvanic)corrosion. This often makes the plugs IMPOSSIBLE to get out. The only way is to drill them out by drilling a progressively larger hole in them until the remaining plug threads are paper thin. Then, use a small awl or scribe to pick them out. Of course, the transmission should be out of the car and the "guts" removed before you do this. That's the hard part.
A drain plug magnet (even if your car is equipped with a magnetic drain plug) is not responsible for your difficulty in removing the plug. These plugs are steel or cast iron and the case is aluminum. Therefore, for some reason or another, the interface is subject to dissimilar metal (galvanic)corrosion. This often makes the plugs IMPOSSIBLE to get out. The only way is to drill them out by drilling a progressively larger hole in them until the remaining plug threads are paper thin. Then, use a small awl or scribe to pick them out. Of course, the transmission should be out of the car and the "guts" removed before you do this. That's the hard part.
