# Muncie M20 transmission



## mysons69 (Mar 3, 2012)

Hello all, I am looking to buy a Muncie M20 for my 1969 GTO and I have a few questions. The person who owns the Muncie had it in a 1969 Camaro.



Does the speedometer cable on a Muncie M20 connect on the passenger side or drivers side of the transmission?

And

Can anyone help me clarify this VIN: 29N102166 
Date code9E19A
I'm pretty sure the 2 means Pontiac but I am not sure about the rest.

Any help would be much appreciated!


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## mbergin (Jun 19, 2012)

Hi. Hope I can help. 

In most cases, the Muncie M20 had a passenger side speedo. 

The P9E19A is the serial number/build date code and deciphers like this:

P=Muncie. 
9= 1969
E19= September 19 ( build date)
A= M20 ratio code. 

Take a look at the casting numbers. A 1969 M20 should have the following casting numbers:
Main case-3925660
Tail housing-3857584


As far as the VIN, it breaks down like this:

2=pontiac
9=1969
N=build plant ID- Muncie. 
XXXXXX- sequential vehicle identification number. 

Due to the wide combination of id’s, stampings, numbers, etc… varied and even GM couldn’t keep track of what was what, it’s best to ID your gearbox visually, taking what is stamped on the box FWIW. 

Hope this helps....

Mike




Sent from AutoGuide.com App


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## geeteeohguy (Feb 2, 2008)

Most Muncies did have the speedo cable on the passenger side. That's because they made a lot more Chevrolets than anything else. For you Pontiac, the speedometer cable needs to be on the _driver's side _of the tailhousing.


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## Rukee (Feb 8, 2007)

:agree Mine has the born with tranny and it's on the drivers side.


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## mysons69 (Mar 3, 2012)

Yeah, from what we have learned (?) from much searching is that the GTO speedo seems to be on the driver's side, which would mean a different tailshaft from having the speedo on the passenger side.
Almost all of the 69-dated trans seem to have the 3857584 tail, which is passenger side speedo.
At this point we're leaning towards going with this just to get the car on the road, and then try to come up with the correct tail or entire trans later. The p/n of this correct tail is still eluding us, however. We suspect it should be 3846429, but have not been able to verify this.
Funny thing about this trans is that the s/n is Pontiac, yet it has the 7584 tail, passenger side speedo. Maybe from a Firebird or such...

Thanks for the input guys.


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## mbergin (Jun 19, 2012)

That's may be the correct tail housing. I have a 1969 GTO with the original Muncie M20 with the tail housing number of 3857584 with the passenger side speedo. Found this on the Internet....not sure if its accurate. 

"Proper identification of the transmission type is absolutely necessary, but sometimes difficult due to several factors. First, GM used several different methods to label and identify transmissions from year to year and model to model. Unfortunately the identification systems seem to have many exceptions, rendering them virtually useless to the restorer. In addition, due to engine and transmission swaps, and modifications that occur over the years many cars do not carry the original drivetrain that they were produced with.
For example, due to interchangeability, a 1969 Pontiac could have a trans case and gears from a Buick and a rear housing (extension) from an Oldsmobile. Several production changes through the years that effect the external appearance may also cause additional confusion when identifying a particular transmission:
1. Both single and dual drain plugs were used.
2. Speedometer adapters were used on either sides of the rear section (extension).
3. Side covers were sometimes secured with studs and nuts, other times with bolts.
4. Input shafts may be fine or coarse spline. Output shafts may be large or small. Combinations of these vary.
5. External shift levers are secured with studs and nuts, others with bolts. Some levers are long and some short.
6. Input shafts may have 1 ring, 2 rings, or no rings at all."


Good luck. 


Sent from AutoGuide.com App


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## mysons69 (Mar 3, 2012)

This is some confusing stuff, I must say. Yours is the best answer I've gotten, in so far as you saying your tranny is original AND that it does have the 7584 extension. I keep coming across random tidbits (not to mention geeteeohguy and Rukee saying so) pointing in the direction of driver's side speedo, but so far no hard evidence (no disrespect to geeteeohguy and Rukee ) such as assembly manual, etc, and no alternative extension number.

From the original post, the trans I was looking at also has the 7584 passenger side speedo, but the VIN starts with a 2, making it Pontiac. At least the case is. Who knows if the extension is original or not.

I ended up getting an M20 out of a '69 Vette, and the PO was pretty certain it was from a now missing numbers matching car. Either way, it also has the3857584 tail. Not a big deal, we'll make it work.

I'm curious though, if mbergin's original M20 has a passenger side speedo, and Rukee's is on the driver's side, does that mean GM really did mix and match, implying either is correct?

I guess my next worry is how much trouble we'll have with the shifter.


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## Rukee (Feb 8, 2007)

The shifter should be the same, and you should be able to run a speedo cable from a chevy that should be longer.


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## Purple Haze (Feb 27, 2011)

*The Holy Grail*

Here's all the info you'll need.... I suggest everyone should save this link to their favorites!!

Identifying Muncie 4-Speeds

The tail shaft as mentioned is what you need. I believe it will be a straight bolt on for any Muncie???


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## Indetrucks (Apr 2, 2013)

Where is the Muncie "P" code located on the tranny?
Can it be located by crawling under the car?


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## mysons69 (Mar 3, 2012)

Well, this is about the best I can figure out...

Rukee has a '65, driver side speedo.
geeteeohguy also has a '65, driver side speedo.
mbergin has a '69, passenger side speedo.

Therefore, Rukee and geeteeohguy must have the 3846429 tailshaft.

mbergin must have the 3857584 tailshaft (this is what I have).

FWIW, I was at a shop a couple weeks ago, they had a '65 up on the lift. I asked if I could take a look. It had driver's side speedo, tailshaft 3846429.

Not that this proves anything, but I 'm feeling a little better about having the 3857584 passenger speedo at this point. Maybe these tables are correct? They pretty much all say tail housing 3846429 was used from 63-65, which jives with what you guys are saying. Maybe we answered a question no one other than me was asking?

Indetrucks, the "P" number (date code) on mine is on the main case, passenger side, just in frint of the tail housing.

Thanks all for your contributions.:seeya:


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## Indetrucks (Apr 2, 2013)

mysons69 said:


> Indetrucks, the "P" number (date code) on mine is on the main case, passenger side, just in frint of the tail housing.
> 
> Thanks all for your contributions.:seeya:


thank you


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## geeteeohguy (Feb 2, 2008)

Every real, unmolested GTO I've ever seen in the past 40 years including the many I have owned has had the speedo cable on the driver's side. Chevrolet's have the cable on the passenger side.


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## ALKYGTO (Mar 29, 2010)

FWIW my original 69 trans has a drivers side spedo cable.


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## hlzabm (May 12, 2017)

I am looking for a 1965 GTO M20 trans dated 11/54-5/65 range


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