Transmission Case 3925660

[Jimmy J.]

Can any one tell me what a transmission with the GM part number 3925660 fits? Thanks in advance. Jimmy

[Joe L.]

Re: Transmission Case 3925660

Jimmy-----

That part number is for the transmission main case originally used for 1968-69 Muncie 4 speed transmissions. While it was originally used for these applications across the GM line, the transmission of which it is a part will fit a wide range of applications. Far, far too many to list here.

[John H.]

Re: Transmission Case 3925660

It will have a "P"-code stamped vertically on the rib at the rear of the passenger side of the main case, and a VIN derivative stamped in the same location on the driver's side; these will identify it and indicate what it was originally installed in.

[Jimmy Johnson]

Re: Transmission Case 3925660

John/Joe were these transmissions ever used in Corvettes? I found 4 of these in a back room of a salvage yard that is going to be liquidated. Jimmy

[Joe L.]

Re: Transmission Case 3925660

Jimmy------

Yes, they were used in Corvettes. The Corvette versions for any given year were exactly the same as the ones used for other Chevrolet (and, most other GM) cars for that year. Transmissions which were manufactured with this case part number were used for 1968-69. However, transmissions as originally assembled with this case will fit any 64-70 Corvette as a direct bolt-in. They can also be used on many other Corvettes with some modification.

[Tom P.]

Re: Transmission Case 3925660

It's true that the 660 case will physically fit the 64-5 as well as through 70 Muncies---------------------BUT, the 64-5 Muncie cases had holes for a 7/8in cluster gear shaft, whereas the 660 case had 1in holes for the cluster gear shaft (the 63 case also had 7/8in holes, but it had some other unique features also). So, as far as a DIRECT interchange, the 660 case will fit 66-74 Muncies. There were three different cases with 1in holes between 66 and 74: 3885010, 3925660 and 3925661. All three will physically interchange. The only difference between the 3 are some external casting variations.
In the Chevrolet line, the Muncie replaced the Borg-Warner T-10 in mid-63. The Muncie was last used in production GM autos up through the 74 models, when it was replaced by the Borg-Warner Super T-10. Some car lines, such as Buick continued to use the T-10 after 63. Also, the T-10 was available as an aftermarket 4sp through speed shops, etc, whereas the Muncie was ONLY available from GM sources.