I have this tranny with these numbers and need help identifying it. they are: 3925660-- 3928764GM1--28G121847-- P8T06
John 66 graemlins/clonk.gif :confused:

Originally posted by jhunt:
I have this tranny with these numbers and need help identifying it. they are: 3925660-- 3928764GM1--28G121847-- P8T06
John 66 graemlins/clonk.gif :confused: 3925600 ~ (casting #) 1968 – 1970 1" Bore Patent Number (main case)

3928764 ~ (casting #) I show a 3978764 as 1970 – 1974 passenger speedometer, 32 spline output (tail housing).

28G121847 ~ (stamped number) the '2' indicates a non-Chevrolet I believe (Chevy is '1' but can't remember Buick/Olds/Pont #'s), '8' is the year, 'G' is the plant, 121847 is partial VIN of original car.

P8T06 ~ (stamped number) Serial number: P is Muncie, 8 is 1968, T is December and 06 is the day. A December date means it was actually built December, 1967 for the 1968 model year.

The 1969 to 1974 Muncies also got a letter (A, B, or C) suffix to indicate M20, M21, or M22 respectively on the serial number. Starting in 1967, the serial number got the year designator.

Looks like a '68 model year trans with a later tail shaft housing.

The "2" in 28G121847 is Pontiac. The correct extension housing for this transmission is 3846429 with the driver's side speedometer fitting along with the smaller 27-spline output shaft. Pontiac used this extension housing on A bodies (GTO, LeMans, Tempest) through 1970.

Thanks fellas
Should this piece fit a 66 chevelle that now has a saginaw tranny as long as I have the correct yoke and clutch plate?
John 66 :confused:

Should fit your 66 fine... You might need to reroute the speedocable though. 1966 Chevelles with the Muncie (and maybe the Saginaw) had the passenger side speedo cable in the trans, and therefore used a longer speedo cable that came out of the firewall/floor on the passenger side... BUT, every 66 Chevelle I have had with a Muncie (that I recall) had a driver-side speedo (replacement trannys)... So it will work just fine...

From the 21,847th 1968 Pontiac A-Body built at the Framingham, MA GM Assembly Plant.