Saginaw Transmission Guide
This GM light-duty manual car transmission was used from model years 1966- 85. The transmission got its name because it was manufactured in Saginaw, Michigan. It has a cast-iron case and extension housing with a seven-bolt bolt side cover. The reverse shift lever is on the side cover.
The Saginaw is often mistaken for a Muncie transmission because the Muncie also has a seven- bolt side cover. However, the Muncie reverse lever is found in the extension housing and features an aluminum case.
Many popular vehicles came equipped with a Saginaw transmission, including Chevy Corvettes, Camaros and Novas which had 300 horsepower or less. Saginaw transmissions were also found on the Pontiac GTO, Pontiac Tempest, Chevy Corvair and Chevy Impala. Vehicles using the three-speed Saginaw had an RPO code of M15 while vehicles with a four-speed Saginaw had an M26 or M27 code. Today, rebuilt Saginaws are popular for racing and street rodding.
Saginaw 3-Speed Identification
There are several gear ratios for the Saginaw's. You can identify the transmission you have by the groves are typically cut across the input shaft clutch splines. To differentiate between a 3-speed and a 4-speed look at the passenger side of the rear cover. A Saginaw three-speed transmission has a code beginning with "S" and a Saginaw four-speed has a code starting with "O." Furthermore, three-speed transmissions have two linkage arms and four-speeds have three arms.
The Saginaw transmission adapters we manufacture will require the installation of a new output shaft. These transmissions are externally shifted and will require shifter components. We make an adapter to mate this transmission to a Jeep Dana 18 or 20 transfer case.
Lubrication and Maintenance
GM recommends using 80-W90 GL4-rated gear lube; 75-W90 is also acceptable. Saginaw transmissions hold roughly three pints (1.5 quarts) of oil. Certain synthetic gear oils may be too thin, so be careful. If using a synthetic oil, it must be approved for yellow metal use due to the brass material in the transmission's synchronizers.
Saginaw 3-Speed Transmission Gear Ratios:
# OF SHAFT GROOVES 1st Gear 2nd Gear 3rd Gear
0 2.85 1.68 1.0
1 2.54 1.50 1.0
2 3.11 1.84 1.0
3 3.50 1.89 1.0
4-Speed Saginaw Transmission Gear Ratios
# OF SHAFT GROOVES 1st Gear 2nd Gear 3rd Gear 4th Gear
0 2.84 2.01 1.35 1.0
1 2.54 1.80 1.44 1.0
2 3.11 2.20 1.47 1.0
3 3.50 2.47 1.65 1.0
Other Saginaw Transmission Technical Specs:
Dates Produced: 1966 to 1985
Manufacturer: Saginaw
Case Length: 9.625 inches
Bellhousing Length: 6.5 inches
Overall Length: 16.125 inches
Case Material: Cast iron
Input Shaft Spline: 1-1/8 10 spline
Input Shaft Length: 6.5 inches
Pilot Diameter: 0.59 inches
Pilot Length: 1 inch
Transmission Weight: 90 pounds