The Bert racing two-speed transmission may be quite different from most other units out there, but its simplicity makes it fairly easy to rebuild.
You won't find anything like it on a street car, but the qualities that make a Bert transmission unique also make it nearly perfect for dirt racing. Simplicity is the name of the game here. Bert Transmission's two-speed trannies are all about cutting down on the number of parts involved and reducing rotating weight. Most significantly, the clutch is actually inside the transmission housing, eliminating the typical clutch and throwout bearing assemblies. There are also only two forward gears and a reverse, and the gears themselves are physically a lot smaller than what you might be used to seeing in a typical four-speed. The net result is a lot less rotating weight burdening your engine as you power out of the corner.
Of course, if you race Late Models or Modifieds on dirt, you probably already know this. Maybe what you don't know, however, is just how easy a Bert transmission is to rebuild. Yes, it is quite a bit different from just about everything else out there (a Brinn transmission is built on the same design principles), but its simplicity also makes it easy to maintain and rebuild.
Gear specialist Jim Cook, of Jim Cook Racing, says barring accident damage or severe abuse, a Bert transmission should last a complete season, or even two, between rebuilds. During a visit to his shop in Concord, North Carolina, Cook showed us how simple it is to inspect and rebuild a Bert using the company's rebuild kit. Because of time constraints, we tore down one customer's transmission and rebuilt a different unit that Cook had waiting for us. To improve efficiency and durability, Cook had the shafts and gears REM polished. He says this won't take a Fifth-Place car and send it to Victory Lane, but it will help reduce friction losses and keep oil temperatures down.
So, if you've got a Bert tranny that needs to be rebuilt, stop making excuses and get to work!
The first steps in the rebuild process are: put the transmission in a clean work area, drain the fluids, and pull the side cover so that you can access the shifter. Take a quick preliminary look aroundfor any obvious signs of damage. | 
The clutch is the small drum at the front of the housing. Using a screwdriver, compress the drum. If the travel, or play, is between 31/416 and 11/44 inch, the clutch packs are probably still good. More than that indicates excessive wear, and the clutch discs will need to be replaced. | 
Here are the components included in Bert's rebuild kit: new clutch friction discs, seals, two roll pins, and a tailhousing bushing. The transmission has several roller bearings, but Cook says the wear on those bearings is so minimal that they rarely need to be replaced. |
Knock out the roll pins holding the shifter forks in position so that you can pull the shifter shafts from the back of the housing. | 
Be careful when pulling out the shifter shafts. An arrangement of springs and steel balls is used as a positive stop mechanism for the shifters and keeps the driver from engaging two gears at once. If you just yank the shafts out, those springs can go everywhere. | 
Difficulty getting the transmission to go into gear can be a sign of shifter fork wear. If the wear pattern on the forks is more than 0.040 inch deep, replace them. |
Pull the tailhousing and remove the gear from the shaft. Check this and all the other gears for signs of wear (e.g., chipped teeth and rounded edges). | 
Remove the C-clips so that you can pull the front bearings and then push the input shaft out of the housing. | 
The reverse idler shaft won't come out until you remove this key on the front of the housing. Use a piece of 1-inch aluminum or brass bar stock to drive the shaft out. |
A large spring keeps the clutch pack engaged and makes it difficult to pull the clutch and its shaft out of the housing. Use a C-clamp to compress the clutch pack so you can pull it out of its location. | 
Once you have the clutch assembly loose in the housing, use a large vise with a set of wide jaws to help you get the entire assembly out of the opening in the rear of the housing. | 
Bert uses shims in the front and back of the clutch shaft assembly to properly locate it in relation to the housing and input shaft. Keep the shims from the front and back of the assembly separate so that you can get them back in the right place upon reassembly. |