A Bert-style two-speed transmission...
A Bert-style two-speed transmission is very popular in dirt track racing because its relative simplicity makes it lightweight and dependable. That simplicity also means it doesn't require a dedicated gear specialist to rebuild it.
The two-speed transmission cuts down on the number of parts, including the standard clutch. Instead, the transmission is included inside the housing. Still, even though it is quite different that what you might consider a "standard" transmission like you would find in a street car, a Bert transmission is easy to maintain and rebuild.
Transmission specialist Jim...
Transmission specialist Jim Cook already had the transmission by the time we arrived. He said the Bert showed normal signs of wear and showed us the reverse idler gear as an example. The edges of the teeth (top) are worn from grinding the gear, and the second row also has a large chip, which probably happened by running the car too fast in reverse. This gear isn't salvageable.
So if you've got a worn-out Bert underneath your car but can't afford to send it off for a refresh, you may want to try a rebuild yourself. All we needed for ours was a rebuild kit and a new reverse idler kit from Bert Transmission. After that, it just takes plenty of rags, a tube of silicone, a parts washer or brake cleaner, and a little time. Let's get to it!
 1. A good check before beginning...  1. A good check before beginning is to insert a yoke into the tailhousing and check for play. If you get more than 1/16 inch of back-and-fourth movement with the yoke 3 or 4 inches out of the end of the tailhousing, you'll need to install a new bushing to keep play to a minimum and eliminate oil leaks. |  2. Here are the components...  2. Here are the components of our Bert rebuild kit. It includes new friction plates, seals, and everything that will wear from normal use. This particular transmission isn't equipped with a ball-spline shaft, so we won't be using the three pieces on the top row. |  3. If the yoke test came...  3. If the yoke test came out OK, you can tap a new tailshaft seal into place. |
 4. Check the output shaft...  4. Check the output shaft to make sure the splines aren't twisted. There are several bearings of all different sizes to be found throughout the transmission, Cook says that if they aren't damaged they only rarely show any signs of wear. If they still roll smoothly, he gives them a light coat of assembly lube and reinstalls them. |  5. The output shaft bearing...  5. The output shaft bearing is held in place with C-clips. After they're installed you can use a hammer and a soft-metal punch to gently tap the bearing into the housing. It's only a slight press fit, so only minor force should be required. |  6. The internal clutch is...  6. The internal clutch is actuated by this piston assembly inside the tailhousing. When rebuilding your Bert transmission, remove and inspect all the pieces for damage and if everything looks OK, reinstall with a new seal to prevent leaks. |
 7. This is the clutch drum...  7. This is the clutch drum assembly. Notice the Torrington bearings and spacers in the background. They're used to properly locate the drum inside the housing, so make sure to keep notes of how many spacers and their thicknesses are used on each end of the shaft holding the drum in place during disassembly. |  8. In addition to the Torrington...  8. In addition to the Torrington bearings and spacers, the shaft inside the clutch drum also has a large spring and two bearing cages. They all should just slide right into place. |  9. Although replacement steel...  9. Although replacement steel disks aren't included in the rebuild kit, they can wear too. They can also sometimes glaze over, so hitting them lightly with 320 grit sandpaper will help. |