I adjusted my TFTC shaker motor this weekend, as the settings on the cpu don't allow for increasing/decreasing intensity. I thought I'd document it here for future reference as I didn't see a lot of info on it on the net.
Take off the two screws holding down the motor's cover.
Once off, you'll notice the motor is quite simple. Two rectangular weights are attached to each end of a spinning axle. The weights attach to this axle with a simple set screw. SO you'll need a small hex allen wrench. You may want to remove the motor at this point via it's own 4 screws holding it onto the bottom of the cab. Or you could just proceed as is. I found it easier to remove it.
Now, the two weights on my motor were aligned together. You'll see what I mean once you take a look at yours. When the weights are aligned together, it makes for the most intense shake. To decrease the shake, remove ONE weight's set screw, rotate the weight 90 degrees, and retighten the set screw in the next set screw opening. Each weight has two possible settings for the set screws. The axle has one divot on it for the set screw to be tightened into. SO, at this point, the weights are now at 90 degree angles from each other. I tried my game and thought it was still a bit too intense.
I then went on to adjust the OTHER weight now, so that the weights were 180 from each other. This basically made the shaker much less intense.
All in all, it's really straight forward once you take off the plastic cover over the shaker. You can also remove the motor assembly (which I did) in adjusting the set screws. It was only held down to the bottom of the pin by 4 screws.
Easy to adjust!