Help to ID 1964-65 Muncie 4 speed

[Ralph Spears]

There is no VIN but main case is casting # 3851325 Tag on side cover#3780800 is it close or wide ratio

[Jimlt4383]

There is no VIN but main case is casting # 3851325 Tag on side cover#3780800 is it close or wide ratio

Ralph,1 ring on the input shift is close 2.20 ratio. 2 rings is wide 2.56 ratio. No rings is m22 on the Muncie factory input shafts.

[MarcDant]

I have a 64 input shaft with 24 teeth with no rings (wide ratio) , the tag that was removed from same tranny that reads 3841435 if i remember correctly was a 3.36 rear ratio. Maybe some one can confirm .

[jeffschevelle]

The 3780 beginning part number does not make sense for a 64 or 65 Muncie trans. 3780 correlates to part numbers originally issued in about 1960 or 1961. Numbers of course can continue to be used for years, but since Muncie's did not first exist until 1963 that would not be the case here. For example, the part number listed in the AIM for a 1964 Chevelle Muncie (wide ratio) is 3841435.

So the tag probably does not go with that trans.

You can at least narrow down the maincase to being original to either a 64 or a 65 trans. 64 maincases have a smaller rounded casting boss on the top rear center of the case (where it is drilled and tapped for the hole for the top center tail housing bolt). 65's have a much larger rectangular boss which looks like 66 and later cases.

[John Brown]

Ralph,1 ring on the input shift is close 2.20 ratio. 2 rings is wide 2.56 ratio. No rings is m22 on the Muncie factory input shafts.

Early Muncies don't follow the same rules as later ones do. I also had a wide ratio 2.56 (325 case) with no grooves on the input.

[Jimlt4383]

Early Muncies don't follow the same rules as later ones do. I also had a wide ratio 2.56 (325 case) with no grooves on the input.

Thanks, do you know when they started using the rings?

[Jimlt4383]

Looks like 63 through 65 had no groove on the m20 and 1 groove on the m21. I did not know that.

[crash]

The 3780 beginning part number does not make sense for a 64 or 65 Muncie trans. 3780 correlates to part numbers originally issued in about 1960 or 1961. Numbers of course can continue to be used for years, but since Muncie's did not first exist until 1963 that would not be the case here. For example, the part number listed in the AIM for a 1964 Chevelle Muncie (wide ratio) is 3841435.

So the tag probably does not go with that trans.

You can at least narrow down the maincase to being original to either a 64 or a 65 trans. 64 maincases have a smaller rounded casting boss on the top rear center of the case (where it is drilled and tapped for the hole for the top center tail housing bolt). 65's have a much larger rectangular boss which looks like 66 and later cases.

The rounded casting boss change over was the middle of Dec. of 1964, well into 1965 production.
I have found several articles stating what Jeff posted, but I check over 100 325 cases and could not find a rectangular boss until late Dec. of the 1964 calendar year, which is 1965 production year

Hope this helps... Crash

[Ralph Spears]

I found out it is a wide ratio

[TAR6569]

Ralph, is the date code stamped in the 64 location by where the side cover mounts? Also, is there a partial vin starting with a T stamped on the edge of the tailhousing where it mounts to mid plate?

[Ralph Spears]

I have photos of 2 stamp locations but i am unable to post pictures on this site send me your email and i will send them to you

[Ralph Spears]

I am able to post photos on every other site but this one unable to figure out how to do it

[TAR6569]

I will send you a PM with my email address

[TAR6569]

Ralph emailed me some photos and we figured it out! Was a 65 M20 out of a Pontiac 233-235 or 237xx body style with 3.55, 3.08, 3.23 or 3.36 ratio axle as it still had the part number tag attached 9780800. This makes sense with the vin stamp on top of the case with no letter for the assembly plant. 308123, which is quite high and P0609 assembly date in the 65 location didn't line up for any Chevy assembly plants. Curious which Pontiac plants assembled the most cars in 65.