 Here's the entire clutch pack...  Here's the entire clutch pack assembly. Note that there are three Torrington-style bearings between the spacer shims (seven in total). Make sure that you remember where they go so that you won't forget one when you reassemble the unit. |  Here's a worn friction disc...  Here's a worn friction disc (left) compared to a new disc. If there are black heat rings on the friction clutch disc, it needs to be replaced. New friction discs are 0.105 inch thick. If your discs are less than 0.095 inch, they should also be replaced. Before installing new friction discs, soak them in type F transmission fluid for at least 30 minutes. |  The steel clutch plates are...  The steel clutch plates are very durable but can get glazed over, which reduces their effectiveness. You can remove any glazing by scuffing the plates lightly with 320-grit sandpaper. |
 Reinstall the new clutch plates...  Reinstall the new clutch plates in the housing, interchanging between the steel plates and friction discs (there should be a friction disc on the outside on both sides). Be sure to replace the Torrington bearings in the same locations. If you forget the Torrington bearings, you will get metal-on-metal contact and the transmission will lock up before you take the green flag. |  The clutch is engaged with...  The clutch is engaged with this piston assembly housed in the tailshaft that actuates on the clutch shaft. When rebuilding the transmission, remove and inspect the components and replace the seal to reduce the chance of developing a leak. |  Before it can be reinstalled...  Before it can be reinstalled in the housing, the clutch assembly must be compressed. You can do this with a piece of threaded rod and a few nuts and washers. Make sure that all the clutch plates slide smoothly in the grooves on the inside of the clutch housing so that you don't bend a plate. |
 Slide the assembly back into...  Slide the assembly back into the housing and use the vise grips to keep the clutch assembly compressed while you remove the threaded rod. |  Now switch back to the smaller...  Now switch back to the smaller C-clamp so that you can slide the clutch shaft assembly back into its proper location and drive the shaft on which it rides in place. |  Another view shows how it...  Another view shows how it fits back in place. |
 Check the play in the clutch...  Check the play in the clutch pack housing again to make sure you have the necessary 31/416 to 11/44 inch of travel. |  Slide the input shaft loosely...  Slide the input shaft loosely into position. |  Reassemble the output shaft...  Reassemble the output shaft into the tailhousing. You can use a gasket on the tailhousing, but Cook says the most dependable way to prevent leaks is simply to use a thin film of silicone. |
 Connect the input and output...  Connect the input and output shafts and bolt the tailhousing in place. Carefully drive the main bearing into the housing and install the C-clips that secure it. |  The shifter forks and slider...  The shifter forks and slider shafts are installed in the reverse order that they were removed. Getting the springs, steel bearings, and the steel spacer in the right position can be a bit difficult because they have to be compressed while you position the slider shafts. Just be patient. |  When reassembling the slider...  When reassembling the slider shafts, remember that the reverse shaft has two notches while the primary has only one. Use plenty of high-pressure lube on the shafts to protect them until the transmission fluid manages to work its way in there. |
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.
 After unbolting the housing...  After unbolting the housing cap, the slider shaft can be removed. Be sure to catch all the stainless steel bearings as they come out. |  The grooves in the shaft in...  The grooves in the shaft in which the bearings ride catch dirt and grit fairly easily. Clean the shaft and relubricate with a good CV joint grease. |  Don't forget to check the...  Don't forget to check the seal. If the shaft has been slammed back into the tailhousing, it is possible for the seal to be damaged as this one has been. Go ahead and replace it. |