4WD, Tank treads and gear ratios.

[sanddrag]

sparksandtabs is mostly right except for a few things I believe.
You shouldn't have to program anything as far as I know. The default program should be able to handle 4 drive motors.

As for matching motor speeds, as far as I know the Vex motors are neutrally timed meaning they spin the same speed in forward and reverse. Also, for pairinbg motors together, it is done all the time in FRC. With identical motors, you are correct in saying that there will be differences but these differences are so extremely small that it is not of any concern. (maybe if you were building some sort of fine clock it would be). In FRC, we even match differnt motors together quite often with no problems.

For the tank treads, I don't know what to tell you without actually seeing the problem. Maybe you can describe it a little more. I wouldn't go spraying them with any sort of lubricant though. If you are looking for more traction out of them, it is possible you could adhere some sort of rubber to each link of the track.

For mounting the wheels, the benefit of having it driven by gears or sprockets and chain is that it is independent from the motor. The motor is supported by it's own mount and the wheel is supported by it's own mount. If you put a wheel right on the motor, you will be side loading it which is not good. I'm not exactly sure what the vex kit offers in the way of shaft couplings but if you put the wheel on it's own thaft that is inline with the motor shaft, then connect the two with a coupling, that would work just fine.