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.
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.
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.
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.
There are two things going on in this photo to take note of. First, notice the lump of black garbage in the bottom of the case. That's metal that has collected to a magnetic disk glued to the case. Cook says it is impossible to clean properly, so he just knocks it out with a chisel and throws it away. If you maintain your transmission properly, you won't need the magnet anyway. Second, it is difficult to tell here, but that muddy mess you see has more water in it than oil and is the reason some of the gears on the main shaft are ruined.
When installing the gears and synchronizer hubs back on the cluster shaft, Cook uses a lithium-based paste for lubrication. It's thick enough that it will still be in place no matter how long the transmission sits before its first use.
