The 645 will replace the stock steering servo. Just make sure that you use one of the screws that come with the servo. The worse that can happen is that you might have to flip the servo reversing switch on your transmitter. I use the stock CEN servo for the throttle and the bake and have had no problems with it at all.
The 645 will drain your batteries slightly faster so you should upgrade to a rechargeable 6volt pack.


rolland