Changing the shift point for different gear ratios
Two-speed adjustments are necessary when changing the gear ratio between the clutch bell and the spur gear. Changing the gears on the clutch bell to a higher number of teeth, and/or changing your spur gear to a smaller number of teeth will give you a higher top speed. This will also take away a little bit of low end punch. This will affect your shift point by making your two-speed shaft turn at a higher RPM, thus causing the two-speed to shift sooner. If you are going to a clutch bell gear that has a lower number of teeth and/or a spur gear that has a larger number of teeth, then the two-speed will react just the opposite. Turn the adjustment screw clockwise for a later engagement, or turn the adjustment screw counter-clockwise for an earlier engagement depending on the need. Adjust the two-speed in small increments. Never turn the adjustment screw more than 1/8 turn at a time before testing the shift point. This is a fine adjustment, and can get way off base quickly if large adjustments are made.
The shift point of the two-speed is not only important for optimum performance on the track, but it is very important for long engine life and reliability of the engine as well. If the transmission is shifting too soon, power will be lost, and the engine will over-heat quickly. If the shift point is too late, then the engine will be allowed to rev too high for too long. This condition can cause many problems like accelerated wear between the piston and sleeve, plug damage, poor fuel economy, and can also lead to very hot engine temperatures.
The prme time for the transmission to shift is at the point before the engine is just about to "wind-out" or "peak". You don't want it to actually reach its peak rpm, but you'll want it to get close. This will allow the engine to clear out, and continue to produce good power on through the next gear ratio.
A well-timed shift point is also important on the track. When the transmission shifts into second gear, there is a noticeable "instant" boost in speed. This boost can upset your truck's handling before and through the turn. This can cause a greater chance of you over-shooting the corner, which adds seconds onto your lap times. For instance, if you're racing on a medium-sized track that has a long straight, but the rest of the track consists of many turns and switch backs, then there is a good chance that first gear will be able to handle all of the infield duties on its own. There is really no need for the transmission to shift until you're on the straightaway. In a situation like this, allowing the transmission to shift in the infield will more than likely hurt your lap times, by increasing the chance of the shift throwing your truck wide in a corner. If the engine is really revving out in an area or two within the infield, then it is ok to allow your transmission to shift; just use good judgment. You may also benefit from gearing up a couple of teeth on the clutch bell to get the rpm down through the infield portion of the track. This, of course, will depend on the track size and layout.
For more information on T-Maxx Performance, tips and tricks check: Steve Slayden\'s The complete T-Maxx performance guide articles.