Saginaw 3 Speed Identification: Have You Known Well About It?

One of the most well-liked and continually utilized transmissions in the racing sector is the General Motors Saginaw 3 speed transmission identification.

The Saginaw transmission is used in a wide range of automobiles. Understanding Saginaw 3 speed identification can help you thoroughly understand your vehicle.

What Is Saginaw 3 Speed?

The non-performance and mid-range performance automobiles from General Motors were equipped with Saginaw three-speed manual transmissions, which transferred engine power to the wheels with a floater design.

The high-performance application code was imprinted on the cast-iron and close ratio transmissions.

The Saginaw company had been creating Saginaw 3-speed transmissions since the 1940s. Some 1964-65 units have bigger gears with the same number of teeth as the 1940-68 units.

This transmission has a side lever shift and is side-loaded with many pressure plate options. All early 3-speed apps contain it.

A three-step countershaft cluster with a tiny step in the middle and an external clutch-style synchronizer mechanically splined for the first and reverse shift gears are distinguishing characteristics.

The greatest issue I have with Saginaw 3 speed is how challenging it is to make a good shift. I was driving a 1955 Chevy with a built 327 and a Saginaw 3-speed.

It looks like a 1965 wide-ratio input shaft with a 1-inch diameter shaft and a 1-inch cluster shaft. I went through three or four different 3 speeds before switching to a Muncie four-speed.

In the end, it was less expensive. It simply couldn’t handle the rapid shift whenever you attempted to crank into it and make the 1-2 shift. Additionally, the shifter would become stuck between the first and the second.

It will be challenging to move quickly with it, but you may utilize it as a driver without a doubt since it suits less demanding applications and has a more lightweight design.

Saginaw 3 Speed Identification

Physical Characteristics

Both Saginaw popular transmission models’ internal components had a seven-bolt cover on the side that sealed the cast-iron case and extension housing.

The brass synchro rings had 30 teeth, and the reverse gears were entirely synchro. The reverse shift lever was mounted on the cover with identification rings.

The casing and main shafts of the Saginaw 3 and 4-speed transmissions are identical.

For this reason, with a few small adjustments, a Saginaw 3-speed’s BW overdrive may be linked to a Saginaw 4-speed.

Early Muncie cases differ from later ones in that they can’t be switched back and forth or have their overdrive put on a Saginaw 3 speed.

Many people aren’t even aware of the Muncie 3 speed, and some mistake it for a Saginaw because they resemble each other.

Both have a 7-bolt side cover, but the patterns differ. The top row of bolts, which includes 3 Saginaw and 2 Muncie, tells the story.

Application Codes

The saginaw transmission identification numbers are a guaranteed way to know what you’re looking at when correctly recognizing a Saginaw overdrive transmission.

The first letter in this string of numbers, which may be located on the transmission casing, will help you know which Saginaw transmission you are looking for.

You will be looking at a 3-speed manual transmission if it begins with an S.

Heavy-duty application codes were located on the passenger flank of the case, following the rear cover, on Saginaw transmissions.

The letter “O” indicated that the wide-ratio transmission had overdrive.

The three-speed transmission’s “S” designation said that it was made in Saginaw, Michigan.

For the three-speed and four-speed, respectively, General Motors assigned the Regular Production Option (RPO) codes “M15” and “M20” internally.

There are transmissions from early and late model years.

The earliest ones have a short main case, perhaps 8″ or so, with four bolt mounting in the side cover, and appear to be produced between 1957 and 1965.

The main casing on the latter models appears longer, and the side cover has seven bolts and can lead to 1,200-horsepower applications.

Gear Ratios

The input shaft’s tooth synchro rings on the Saginaws allowed for easily identifying their various ratios. The Saginaws 3 speed gear ratios come in a variety.

The groves that are normally cut across the input shaft clutch splines can be used to determine your gearbox type.

It’s simple enough to assess the ratio immediately by shifting the machine into the first cluster gear and counting how many input shaft turns correspond to one complete output shaft turn.

Start by setting both selectors to neutral, which for the selections on the side covers is straight up and down in position 12-6.

Hold the output shaft while attempting to crank the input shaft to confirm.

In neutral if the shafts are not locked.

The first gear will now be engaged when you spin the rear selector counterclockwise, allowing you to check the ratio by rotating the output shaft a full turn and counting the turns on the input shaft.

Saginaw 3 Speed Vs Saginaw 4 Speed: Which Is Better? 

The three-speed and the four-speed trans, which I have owned, have an identical 1:1 ratio in high gear. Thus there is no difference until you are there.

Due to the lower gear ratio, the four-speed has more jump off the line and bell housing than the three.

However, the primary distinction that puts me firmly in the four-speed transmission is that the three-speed did not synchro-mesh between the second and first with less demanding applications.

Although most people favor the 4-speed, the 3-speed Dearborn gearbox that came standard in these cars is more powerful.

Additionally, most 3-speed cars were not abused as much as 4-speed cars. Therefore they typically have their original engines remaining in place.

FAQs

Why Does My Older Car Have Only 2-3 Speed Transmissions While Newer Vehicles Can Have Up To 10 Speeds?

The quick answer is that the engine block emits less pollution when operating within a predetermined power range established via extensive testing.

By adding extra gears to the transmission to keep the machine working in the ideal power range all the time, car mugs managed to keep their engine design and manufacturing methods stagnant.

Why Did Early Auto Manual Transmissions Only Have 3 Speeds?

For standard passenger car use, that was all that was required. The 3 or 4 gears cost substantially less than purchasing more. Making quality equipment was very difficult and expensive.

Machines had to be operated entirely manually, and they were orders of magnitude less accurate and advanced than modern machinery.

Can A 3-Speed Automatic Transmission Go For Long Drives At Highway Speeds?

Certainly, yes. Every automatic transmission had two or three speeds when the Interstate system began to be constructed.

As long as the final gear ratio is acceptable, the automatic transmission’s number of rates is irrelevant when traveling on the highway.

Conclusion

Now that I’ve given you some indications on Saginaw 3 speed identification, the next time you have questions regarding your automobile, you’ll know what you want and what to look for.

A skilled mechanic or transmission expert can help determine whether your vehicle has a Saginaw 3-speed transmission.