[nighterfighter]

You would want 5 encoders, if you were powering each wheel separately. But if you aren't going to power each wheel separately, that is a non-issue. I'd imagine you would want 3 total, for drive. One for the left side, with the encoder attached to the gearbox output shaft (Well, the little doohickey that sticks out for encoders), same thing for the right side, then one encoder on your center motor (for the H drive). (Not necessarily on the motor itself, of course. But I'm sure you know where to put it.)

Even if you wanted to use more than 5 or 6 encoders, without expanding the DIO ports on the roboRIO, the Jaguars DO have a built-in interface for encoders, that are accessible via CAN. (The Talons might have them also, you'll have to look that up).