Muncie transmission - Pontiac GTO Forum
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post #1 of 36 (permalink) Old 12-12-2013, 10:54 AM Thread Starter
 
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Muncie transmission

Hi!

I want to change the oil in my Muncie. Can you tell me which fluid and how much of it will be needed to do it?
And are there any things I should know for this job? I'll search it for a drain plug and if I can't find it I might have to use the fill plug to get it out and fill it up until the oil level reaches the fill plug again?!

Not sure if it's a M21 or M22.. does this make any difference regarding the fluid?

Chris
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post #2 of 36 (permalink) Old 12-12-2013, 11:05 AM Thread Starter
 
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Okay just checked the car.. I don't have a drain plug.. just the fill plug. This makes it hard to change at home.
Either way.. I should know what fluid and how much? And should I have the oil sucked out, fill in some new, drive around 10 minutes and change it again to get rid of all the old fluid or is there another "trick"?
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post #3 of 36 (permalink) Old 12-12-2013, 12:41 PM
 
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3 pints of 80/90 weight gear oil. To drain, take out the 4 bolts holding the trans to the bell housing and roll trans to drain it out of the fill hole. Bolt it back up, and fill until it just starts running out of the fill hole.
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post #4 of 36 (permalink) Old 12-12-2013, 01:48 PM Thread Starter
 
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Thanks. Syntetic oil?
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post #5 of 36 (permalink) Old 12-12-2013, 03:03 PM
 
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3 pints of 80/90 weight gear oil. To drain, take out the 4 bolts holding the trans to the bell housing and roll trans to drain it out of the fill hole. Bolt it back up, and fill until it just starts running out of the fill hole.
ON mine, you would also have to unbolt the shifter and speedo cable. ?
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post #6 of 36 (permalink) Old 12-12-2013, 03:31 PM
 
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I've never tried this, but it seems to me that method of rolling on to its side might require removing the cross member and supporting the back end of the engine. Like I said, have not tried it. I changed the fluid in mine by using a hand vacuum pump to remove the old oil. And no, I do not think the synthetic oil is recommended. Should be about 40 oz, but like the gentleman said earlier, it is full when it runs out the fill hole. Regards, Matt

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post #7 of 36 (permalink) Old 12-12-2013, 04:24 PM Thread Starter
 
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Good to know, thank you.
I don't like the idea of rolling the transmission, I'll search for a vacuum pump to remove the old oil. Maybe I'll do it twice (first the old oil, then the new oil after driving it some minutes).

I'll search the shop over here for oil's and see if I can find 80/90 (non synthetic). If I have no luck I'll tell you what I can get.
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post #8 of 36 (permalink) Old 12-12-2013, 04:55 PM
 
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Chris, Lucas is a great brand of gear oil. Matt

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post #9 of 36 (permalink) Old 12-12-2013, 05:14 PM
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I just suck the old oil out with a suction gun. Easy as pie. Never needed to unbolt the trans, unbolt the shifter, unbolt the trans mount, disconnect the speedometer, etc. What a lot of work that would be! 80-90 mineral based gear oil, until it comes out of the filler hole. A bit less than 2 quarts. Never use synthetic in a Muncie....it will shift poorly. M22 is the only early Muncie with a drain plug. You probably have an M20 transmission.....M21's are pretty rare and only came with cars that had 3.90 gears and steeper.
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post #10 of 36 (permalink) Old 12-12-2013, 08:01 PM Thread Starter
 
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Is there a easy way to see if it's a M20 or M21? My 66 GTO has a 69 rear end (9795084)
so it's hard to say what was in there. I was told my rear end is also pretty rare.

I'll try it like you said, suck it out and fill it till it comes out again.

It will be 80/90 mineral based, maybe from Lucas if I can find it. What about 90 oil or I think somewhere in my garage is a bottle of 75/90...
No matter what, I won't use synthetic, thanks for that information. How often do you change transmission oil?
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