Pontiac Manual Transmissions

by Rick Gonser and Larry Gorden

August 2005,  Updated Dec 2009, Oct 2011

Pontiac outsourced transmissions since day one, using Olds for the Hydra-Matics and Buick for their 3-speed transmissions.  Pontiac first offered a 4-speed in 1960.

Year UPC Pontiac 3-speed Transmissions Year UPC Pontiac (GM) 4-speed Transmissions
1936-55 M11 Buick Light-Duty 1960-64 M20 Borg-Warner Early T10 Wide Ratio Released Jan 1960
1956-57 M13 Buick Heavy-Duty 1963-64 M21 Borg-Warner Early T10 Close Ratio
1958-64 M11 Early Muncie Light-Duty 1964-71 M20 Muncie Wide Ratio (1st Design -Late '64)
  M13 Borg-Warner T85 Heavy-Duty M21 Muncie Close Ratio (1st Design - Late'64)
1964-70 M13 Ford Heavy Duty Top Loader (Late '64) 1968-72 M22 Muncie Close Ratio "Rock Crusher" Heavy Duty
        1973-74 M20 Saginaw iron case
          M22 Borg-Warner Super T10 iron case

UPC = GM Universal Product Code.

See http://www.teufert.net/trans/man-hist.htm  for a list of transmissions by year and some good comments.

See  http://www.yearone.com/updatedsinglepages/id_info/muncie.asp for info on 4-speed transmissions


1955 & Earlier Light Duty 3-speed Standard Shift Transmission.

The light-duty Buick trans was used by Pontiac in 1955 and earlier years.  It is easily distinguished by it's small physical size and 5-bolt top cover.  On a scale of 1-10, with "7" being a Muncie M22, the light-duty B-O-P selector is rated as a "4"

The physical size of the sliding gear is ≈ 0.5", which is not very big.  This trans will fail under excessive torque, as the miniscule slider and corresponding cluster gear(s) are simply not strong enough.  High torque forces the slider away from the cluster, and a broken gear tooth is inevitable...


Light Duty Buick, Tail shaft shorter than Pontiac


1956-57 Heavy Duty 3-speed Standard Shift Transmission.

Pontiac installed the Buick heavy duty 3-speed transmission in 1956-57.  The heavy-duty trans is easily distinguished by it's large physical size and 6-bolt top cover.  On a scale of 1-10, with "7" being a Muncie M22, the Heavy-Duty B-O-P selector is rated as an "8"... 

The physical size of the sliding gear is ≈ 1", which is probably too big.  This trans is nearly unbreakable, but the large size of the gears with their nearly straight-cut teeth, slows shifting @ rpm.  I have used this trans behind a 450" JBP motor that produced 485 hp @ rpms.  No problems, since the big stroker's power falls off at 5,100...



1958 and Later Heavy Duty 3-speed Standard Shift Transmission.

The Buick trans was superseded in 1958 by the B-W T85, which is not quite as strong.  According to John Sawruk, the noise and/or gear whine of the old Buick brought about it's demise.  B-W T85s have 22O helix-cut gears, making them quiet as a mouse.  One of the differences between M22s and M20-21s is that the Muncie engineers went back to Buick thinking, removing the high-helix gears.  So, if you've ever ridden in a car with an M22, they sound a lot like the old Buick trannies...

Jerico Transmission.

For drag racing at eliminator levels, most stock trannies won't cut it.  So, those who can afford it use the Jerico.  Note the size and cut of the gears.  Jerico Engineers were also influenced by the old Buick design.  BTW, this box is rated as a "10", just like Bo Derek <grin>, and Jerico owners could care less about the noise...

Transmission Interchange.

The Pontiac bell housing was the same for 1956-57 with a unique interface to the Buick heavy duty 3-speed transmission.  In 1958 and later years, Pontiac used the "standard" transmission interface used also by Chevy and other GM makes.  So you can bolt up a later Pontiac or Chevy transmission onto an earlier Pontiac bell housing (back to 1958).  For example, a '65 Corvette "Rock Crusher" M22 4-speed will bolt up to a 58 Pontiac bell housing.  Of course you have to be concerned about drive shaft length, yoke interface to tailshaft, linkage, speedometer cable length, etc.  But the transmission bolts up to the bell housing.

1958-60 (Left) and 1956-57 Pontiac Bell Housings

Tremac  5-speed Richmond or Richmond 5 and 6-speed six-speed transmissions are also bolt-on compatible to the 1958 and later bell housings.  See http://www.5speedtransmissions.com/5sp_comparison.html for a comparison of Tremac and Richmond 5-speed transmissions.

Suppose you want to install a later 4-speed or 5-speed into your earlier 1955-57 chassis.  Bell Housing to engine block interface was the same for 1955-60.  So bell housings interchange on engine blocks within those years. 

1956-57 and 1958-60 Bell Housings

The 1958-60 bell housing will bolt up to engine blocks back through 1955 -- which allows for installing later standard transmissions.  Even though the 1958-60 bell housing bolts up to the earlier engines, the motor mounts are not positioned in the same place as the earlier 1955-57.  That problem can be solved by using a cross member for 1956 Strato-Flight (controlled coupling) Hydramatic or 1957 Hydramatic.  That crossmember has rear motor mount points a little too far outboard but the problem can be easily rectified by making an adaptor pate for each side something like this.


Brian Deffenbaugh photos.

See this link for Brian Deffenbaugh's installation of a Tremac 5-speed in his 57 Pontiac.