The stock Saginaw case right...
The stock Saginaw case right out of the junkyard and with the worst of the mud knocked off. As a three-speed trans, it's relatively small and the rotating mass is light for a stock unit.
When you think of the little Saginaw transmission, your first thought may not be racing-but maybe it should be. After all, if you're racing a Street Stock class that requires you to run an OEM transmission with few modifications, a Saginaw may be your best bet.
Lots of entry-level racing classes have rules intended to keep racers from using expensive high-end parts or spending lots of money modifying stock pieces. As a result, the rulebook often says you have to run a transmission that appeared as original equipment in the car you are racing and all forward gears, as well as Reverse, must be operable. We've even heard of racetracks that have put in a $250 claim rule for transmissions.
If that's the case, then the Saginaw-with just three forward gears-already has a lighter rotating mass than just about any other trans you'll find. They appeared in a wide variety of General Motors products, including Novas, Camaros, Firebirds, vans, trucks, and others. So finding a core in a junkyard is still relatively easy. It will also bolt right up to a standard Chevy small-block bellhousing.
As a longtime driveline specialist,...
As a longtime driveline specialist, Cook knows all the tricks. This transmission probably came out of a truck or van and is made for a heavier-duty application. Cook says you can shave approximately a pound-and-a-half by shaving off the pad for the fifth bolt on top of the case. This isn't used when mating the transmission to a standard bellhousing.
Another difference you might...
Another difference you might find is the size of the front bearing retainer. Late-model units use the smaller retainer that's 4.685 inches in diameter (on the right). Truck and van transmissions used a larger retainer that won't fit in a standard clutch/bellhousing assembly. If you happen to get a transmission with the larger retainer, you can save a buck by cutting the flange side down in a lathe instead of going out and buying a new one.
If you are trying to use a...
If you are trying to use a transmission you just pulled out of a car, or one that has been sitting around the shop for a while, pull the side cover and squirt some oil between the gears on the main shaft. The standard oil level doesn't cover this shaft and over time the oil can drain out. The shaft only gets splash oiling and will burn up if you stick the transmission in a race car and take it right out on the track without the proper preparation.
After pulling the front bearing...
After pulling the front bearing retainer, the next step in the teardown process is to separate the tailhousing. The trick to getting the tailhousing off is to remove the C-clip that locates the reverse idler gear and pull the gear forward before sliding the tailhousing and gear assembly out.
Apparently, while this transmission...
Apparently, while this transmission has been sitting it has drawn moisture. You can see the effects on the gear teeth. These gears will have to be replaced. You can grind the crud off, but it would still leave pitting and the transmission will never be right.
When pulling the gears from...
When pulling the gears from the cluster shaft, be aware that there is a snap ring hidden practically in the center of the cluster. Pull the gears from the cluster shaft one at a time and if one seems stuck, check to make sure you aren't missing a snap ring.
And finally, it's dead simple-at least as far as transmissions go-so just about any mechanically minded person can rebuild one if he or she is careful. With that in mind, we dragged the camera over to Jim Cook Racing Transmissions and got some shots while he tore down and rebuilt a transmission for a Street Stock racer. Cook also shared a lot of quality tips for working with these transmissions which we will pass on to you.
One quirk of the Saginaw is that the cast iron housing is quite heavy. But fortunately, it mounts low and in the center of the car, so if you're going to have to use heavy components, this is definitely the place to do it.
If you do consider rebuilding your own Saginaw, just make sure to take plenty of pictures during the teardown. This will help you remember where everything goes when it comes time to put it back together. You should be able to find stock replacement parts at your local parts house or even a Chevrolet dealer, but Cook also has rebuild kits available with upgraded components specifically for Saginaws. That way you can get just the stuff you need and don't have to worry if the 16-year-old kid behind the counter was looking at the right screen on the computer when he pulled your parts.
With the Saginaw, there is...
With the Saginaw, there is no synchronizer for Reverse. This means you will see wear on the reverse side of the synchronizer assembly (left) on any Saginaw that has seen normal use. You won't be using Reverse much anyway, so don't worry about it. But if you see the same amount of wear on the forward side of the synchronizer assemblies, they will need to be replaced. The synchronizer on the right side of this photo is still good.
Inspect the cluster shaft...
Inspect the cluster shaft for pitting. This shaft is good, but if you see pitting it will need to be replaced, or else it will destroy the needle bearings that ride on it.
Use a drift to knock out the...
Use a drift to knock out the reverse idler shaft. Note that this shaft only comes out one way as there is a Woodruff key that locks the shaft in place at the back of the housing.
Cook keeps a large inventory...
Cook keeps a large inventory of gears on hand, so being forced to trash the gears from our teardown transmission didn't slow us down. You can get by simply cleaning the gears, but Cook prefers to media blast them as well. He says this helps cracks or other signs of damage show up more readily so you can spot a potential problem before it gets into the transmission and causes bigger troubles.
Cook also has a lightening...
Cook also has a lightening program for the gears, as you can see on the left. When done to the two main gears, he says this cuts about 1.25 pounds of rotating weight without reducing strength. Cook doesn't recommend this for rookie drivers or back-of-the-pack teams, saying that there are better ways of spending your money. But for race teams competing for wins and championships, this, along with his gear-polishing program, can improve the transmission's efficiency and, in turn, improve lap times.
Before putting together the...
Before putting together the synchronizer gear assemblies, coat the teeth with engine assembly lube.