Saginaw Transmission Rebuild - Drivetrain

The brass synchronizer rings are designed to wear first to save the other parts. If you see wear like this on the left, it's time to replace it. The ring on the right has relatively no wear and is still good.

One of the reasons for a severely worn synchronizer ring is broken synchronizer keys like you can see on the top row. Before rebuilding, make sure the grooves cut into the keys are also clean.

As you can see in this photo, the keys hold the synchronizer hub together, and a spring clip-in turn-holds the keys in place. There is a ring like this on both sides of the hub.

Before trying to install the roller bearings, apply thick grease to the inside of the hub to help hold the bearings in place.

Here's another trick Cook often uses in his racing transmissions. On the right is a standard, OEM replacement bearing. On the left is a used max-load bearing out of a NASCAR Sprint Cup transmission that has been used less than 500 miles. The Cup bearing is better in every way than the stock piece, and the price for a new one reflects that. But Cook has many contacts and can find these bearings after they have been replaced in rebuilds-it's one of the perks of operating in the heart of NASCAR country. The bearings are still practically new and Cook can sell them cheaper than you can purchase a new OEM bearing.

The tailhousing bushing is replaced to reduce play in the tailshaft and reduce leaks.

A 3/8-inch freeze plug is perfect for plugging the hole where the speedo gear and shaft used to go.

Here's a shot of the Woodruff key that locks the reverse idler shaft in place. It's easy to forget during reassembly-so don't.

One of the synchronizer rings mates between the cluster shaft and the main shaft assembly. To keep it from falling out, Cook dabs a little grease in the synchronizer hub to hold it in place.

Cook prefers to use silicone instead of gaskets. After years of use, he's found the silicone seals these old cast housings better, and it also tightens up the fit which helps improve the tolerances, which can become looser after lots of use.

When reassembling the transmission, remember to leave the C-clip off the reverse idler gear so that you can slide it back enough to get the main cluster into the housing.

Here's a shot with the C-clip now installed and holding the reverse idler gear in position.

When installing the tailhousing, don't forget to add a bit of silicone to the bolts to prevent leaks.

The completed interior assembly.

Don't forget to replace the seals on the side cover for the shifter mechanism. They are exposed to the elements and likely will go bad.

Here's the shifter assembly inside the cover. Cook advises you take a close look at the detent tensioner spring. It can weaken over time and be a reason your freshly rebuilt transmission won't stay in gear. If it appears stretched or weak, go ahead and replace it instead of taking a chance on it.

Silicone is also used to seal the side cover.

The completed transmission. Cook uses this homemade tool to check the shifting action between the gears. You can use an adjustable wrench, but it isn't a bad idea to bolt up your entire shifter mechanism just to make sure everything is in proper working order before you go to the trouble to install it in your race car.