Can someone Id this munci for me?

numbers on side cover w/7 bolts drivers side
GM 383170

numbers on right side case 3851325

numbers on right side tail GM 3846429

numbers on top main case 5Z107551

First, it's Muncie ;)

3831707 1963-1965 Early side cover stud type shift shafts (I think you missed the last '7')

3851325 1964 –1965 7/8" Bore Patent Number

3846429 1963-1965 Regular thick web, driver speedo, 27 spline


Can't help with the last set (5Z107551). Are they all together? Stamped or cast? Could be a derivative of a VIN of the car; 5 being 1965, Z being Fremont, and the last 6 matching the VIN. :confused:

yes the numbers are all together on top they are stamped.
Any way of telling if this is a "rock crusher" or not?
I want to install a rcihmond 5 speed and was hoping to recoup some cash from the munci.

Chances of it being an original 1965 rock crusher are slim to none since only 20 were reportedly made. If there are no circular grooves on the input shaft it is most likely an M20 wide ratio unit, one groove would be an M21. The 5Z107551 is the partial VIN for a 1965 Fremont built car.

thanks,
it has 1 groove on the diameter of the input shaft. Just the way it drove makes me think its definitly a close ratio.
m21?
Also anyway of telling the gear ratios and approximate value of this trans?
Should I keep it in the garage incase I ever sell the car?

From the VIN, I would say it is from an early 65 built car and if your's is a 66, it is not from your car. Most of the advice on this site advises not to pay more that $250.00 for a used Muncie. Maybe it could be matched up to someone's car on this site.

ok, I thouht it had a groove on the input shaft.

But after looking on ebay on some other munci's I noticed the groove I was looking at is on the front pilot of the input shaft and not on the splines.
So, no groove on the input shaft.And close ratio, what does this mean?

Like I said it definitly drove like a close ratio.
Is there any way to tell what I have?

I have pictures I can email but not sure how to get them on this forum.

"Most of the advice on this site advises not to pay more that $250.00 for a used Muncie."............_If anyone has a used muncie for 250.00 PLEASE PLEASE email me!......

Originally posted by 66dream:
ok, I thouht it had a groove on the input shaft.

But after looking on ebay on some other munci's I noticed the groove I was looking at is on the front pilot of the input shaft and not on the splines.
So, no groove on the input shaft.And close ratio, what does this mean?

Like I said it definitly drove like a close ratio.
Is there any way to tell what I have?

I have pictures I can email but not sure how to get them on this forum. From my info, it's a wide ratio M20 if there are no grooves - The 63-65 M20's had a different gear set than later models; 2.56/1.91/1.48/1.00 vs. 2.52/1.88/1.46/1.00. Reverse is 3.16 vs. 3.11 as well. Check the input shaft tooth count. The M20 will have 24 teeth, the M21 has 26 teeth. But, since the stamped number (5Z107551) is the VIN derivative, it's an early 65 unit. There should be a month/day stamping on the unit (mine is stamped right next to the side cover) - something like "P1025" for October, 25. The 63-66 years only got month/day, 67-68 added the year and the month became a letter (ie P8R25 for October 25, 1968). From 1969 on, a letter suffix "A", "B", or "C" was added to denote M20, M21, or M22 such as P0R25B for a 1970, October 25 M21. All Muncies had the leading "P" letter.

ok I looked and my munci has 10 splines on the input shaft
also has P1109 stamped on the case.
Does this mean anything?