What's the slipper clutch for and how do I adjust it?
All competition buggies and trucks have transmissions equipped with a slipper clutch. On a transmission without a slipper, the spur gear is keyed directly to the top shaft of the transmission, which drives the rear axles through a gear train and ball differential. On a slipper-equipped transmission, the connection of the spur gear to the top shaft is made through an adjustable friction coupling that allows some slippage.
The slipper, used correctly, both improves performance and reduces wear and tear on the transmission:
• The slipper reduces wheelspin as the car accelerates from low speeds, so the car accelerates faster and is less prone to spin out exiting turns on slick tracks. The slipper also gives more sure-footed landings after jumps, so the car handles rough sections and jumps better.
• The slipper reduces sudden forces on the inside of the transmission, especially on the ball differential.
The slipper is a fussy topic. It takes awhile to learn when to loosen the slipper and when to tighten it. Most beginners set the slipper too loose, which makes the car easier to drive but slower overall.
Before you start adjusting the slipper, you must double-check the diff adjustment. Remove the gear cover. Tighten the slipper all the way so it won't slip. Hold both the spur gear and the right rear tire with your right hand, and try to turn the left rear tire with your left hand. It should be quite hard to turn. If the left rear tire turns with moderate effort, with the transmission top shaft stationary as the left rear tire turns, tighten the diff and repeat.
Now loosen the slipper adjustment a few turns, hold both the spur gear and the right rear tire with your right hand, and turn the left rear tire with your left hand. It should not be extremely easy to turn the tire, but not be extremely hard to turn it, either. Fiddle the slipper adjustment to get it into the right ballpark.
Now put the car on the track pointing toward you. Press down on the car and punch the throttle on-off. Listen to that sound -- that's the slipper slipping. Feel how much forward drive the car has. If the forward drive is weak you need to tighten the slipper.
Keep the car on the track pointing toward you. Back away a couple of feet and punch the throttle on until you catch the car. The slipper sound should last only for about a foot -- it should stop before the car reaches you. (It takes practice to hear the slipper sound among all the other sounds, especially the sound of slipping tires.) If it slips more than this, tighten the slipper; if there is no slip at all, loosen it.
Go out and drive the car. If it is working well, bring it in and feel the adjustment again by turning the left tire. Learn how hard the tire is to turn. This will help you get closer to the right adjustment next time you have to adjust it from scratch.
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