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Hi

I have a 1967 Camaro, thats originally a 6 cyl car, but now has a 327 with a Muncie Tranny in it, I have a bunch of part numbers and serial numbers off the tranny and I was wondering if someone could tell me if it is a Rock Crusher transmission. the numbers off the case are:

3857584
P9B12A
3925660
3088336 us pat No.
3950306

They guy told me it is a Rock Crusher, but I would like to know for myself if it really is.

Thanks in advance!

Brad :)


PS sorry about posting the wrong forum area :-(
 

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You have an M-22 "rock crusher" hybrid. Part #3857584 is an extension housing from 1966 and 1967. This is the housing that I have. Part #3950306, is a sidecover casting from 1969. Part #3925660 is a main case from 1968 and 1969. M-22's have the 3925660(or 61) main case.

Unfortunately, the web site I used a few years ago for this info is no longer running.
 

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muncie

quote:part #3925660 is a main case from 1968 and 1969. M-22's have the 3925660(or 61) main case,

This is not a true statement 345 coupe.

The part #3925660 is the casting for any muncie in the 68/69 model year.

The 3925661 number is for all muncies from 1970 until they stopped production in 1974

All m20, m21, m22 transmissions used the same case.

Keith
 

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K-star;

The information I got was from a web site. It gave three different case casting #s, and stated that all Muncie data said the M-22 came with the #3925661 case in 68 and 69 and #3925660 casting in 70-74. The site did not differentiate among the M-20 or M-21. It specifically mentioned the two part numbers for the M-22 though. I do not claim to be an authority. I was just relaying info that I had downloaded.
 

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muncie

Sorry 345 i do not know where the little smiley face with the tongue sticking out came from but i did not put it there..... I promise....

I have seen many web sites with wrong info on the muncie transmissions. I am also not an expert but i have been rebuilding them since 1980... Sometimes i have found the people writing the info on the sites are just typing and they can get the facts wrong....

The site is correct in the fact that all m22 came with those case numbers... But the m20 and m21 also used those same cases.. In fact there are no other case numbers for the muncie in those years...

Again i am sorry if my first post sounded wrong i ment no harm by it just trying to clear things up.....

Keith
 

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muncie

p9b12 =p=muncie 9= 69 b=feb12=day12 3925660=maincase# 3950306=sidecover 3857584=tail housing k-star is on it im not sure but i think you can count the input shaft grooves like one groove 2 grooves or no grooves i dont think the rock crusher had any grooves but im no expert i think the cluster gears are more angled than on the 20/21s giving it the name rock crusher its louder because of angle this is what ive found out on looking mine up hope this might help you mike in indy.
 

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220?

Muncies have been around so long that when it came from the factory it might have been a 220 rock crusher but who knows now.Take the side cover off look at the gears.If they are straight cut and if you take the first gear main gear and divide it by the counter gear for first gear you answer your own question.They called them rock crushers because they are very noisy.They sound like a blower engine winding up in first gear.Dont put to much into the casting #'s beacause if the person selling is a scammer and you dont know that much about it he can pawn it off as a rock crusher even if the casting #'s say that it is.You can inter change alot on the muncies and someone who is savy can change alot in the trans.The casting #'s can tell you that it is a rock crusher when in fact it is not because they have changed all the gears out.
 

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MusclecarBob said:
i have a muncie in my 69/442, its a factory 1 of 550 made 3speeds , i have it in the trunk, in the belly is a muncie 4spd
i'm trying to id it please help

i see
585t584 gm
3088336

3985660
I'm answering you here and not via email so that the forum may get something out of any forthcoming info.

Check the casting number again- it might be 3925660, not 3985660.

On the input shaft, are there any circular grooves cut across the splines?
 

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MusclecarBob said:
YES thats the casting number
and it looks like 2 grooves are in the input shaft so???

m-21 with an m-22 case? or m-22?

regards bob
M-20. Probably a '68 or '69.

2 GROOVES

Ratios
2.52 1ST.
1.88 2ND.
1.46 3RD.
1.00 4TH.

I've heard (never seen, though) that there are exceptions to this- but don't count on it.

Good luck.
 

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Differential/Driveline
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At least that will be a start! I've seen some pretty funky deals over the years with guy's mix and matching parts, like a Trans that had the Big output and a course input{not a crusher}. To be a real one:
1,Cast numbers must match
2, 32 spline output
3,26 Spline input shaft.
 

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MusclecarBob said:
muncie site says that all 3985660. are 70-74
when i bought the 69/442 it was suose to be a m-21 with m-22 gears
Could you post the addy for that site? Thanks.

BTW, I was using the 3925660, not 3985660 for the casting number, thought that's what you meant when you said, "YES thats the casting number".

You can pin it down to either a close or wide ratio by counting the turns in first gear.
 
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