The Bert racing two-speed transmission may be quite different from most other units out th
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!
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The first steps in the rebuild process are: put the transmission in a clean work area, dra
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The clutch is the small drum at the front of the housing. Using a screwdriver, compress th
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Here are the components included in Bert's rebuild kit: new clutch friction discs, seals,
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Knock out the roll pins holding the shifter forks in position so that you can pull the shi
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Be careful when pulling out the shifter shafts. An arrangement of springs and steel balls
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Difficulty getting the transmission to go into gear can be a sign of shifter fork wear. If
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Pull the tailhousing and remove the gear from the shaft. Check this and all the other gear
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Remove the C-clips so that you can pull the front bearings and then push the input shaft o
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The reverse idler shaft won't come out until you remove this key on the front of the housi
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A large spring keeps the clutch pack engaged and makes it difficult to pull the clutch and
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Once you have the clutch assembly loose in the housing, use a large vise with a set of wid
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Bert uses shims in the front and back of the clutch shaft assembly to properly locate it i
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Here's the entire clutch pack assembly. Note that there are three Torrington-style bearing
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Here's a worn friction disc (left) compared to a new disc. If there are black heat rings o
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The steel clutch plates are very durable but can get glazed over, which reduces their effe
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Reinstall the new clutch plates in the housing, interchanging between the steel plates and
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The clutch is engaged with this piston assembly housed in the tailshaft that actuates on t
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Before it can be reinstalled in the housing, the clutch assembly must be compressed. You c
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Slide the assembly back into the housing and use the vise grips to keep the clutch assembl
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Now switch back to the smaller C-clamp so that you can slide the clutch shaft assembly bac
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Another view shows how it fits back in place.
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Check the play in the clutch pack housing again to make sure you have the necessary 31/416
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Slide the input shaft loosely into position.
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Reassemble the output shaft into the tailhousing. You can use a gasket on the tailhousing,
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Connect the input and output shafts and bolt the tailhousing in place. Carefully drive the
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The shifter forks and slider shafts are installed in the reverse order that they were remo
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When reassembling the slider shafts, remember that the reverse shaft has two notches while
Don't Forget the Splines
Because the rear ends in dirt cars often see extreme articulation, many racers use Bert's ball-spline tailhousing. This innovation allows the tailhousing shaft to extend several inches without allowing dirt and sand to invade the housing when the shaft slides back into place. Cook recommends disassembling and cleaning the ball-spline shaft and housing after every two to four races.
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After unbolting the housing cap, the slider shaft can be removed. Be sure to catch all the
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The grooves in the shaft in which the bearings ride catch dirt and grit fairly easily. Cle
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Don't forget to check the seal. If the shaft has been slammed back into the tailhousing, i
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Bert Transmission
St. Constant, Canada
PQ, J5A 2E
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Jim Cook Racing
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