Rover Build motor/esc help.

[sendep7]

I'm building a rover on a traxxas trx-4 as the base platform.

steering via servo works fine.

The on board ESC seems to take a pwm or ppm input? and is reverseable. It works fine from a servo port, but i cant seem to get it to do anything from the s1 esc signal port? is this becuase of some protocol mismatch? can i convert it to pwm/ppm?

i'd love to just keep the onboard ESC so i can revert it back to factory when i feel like it.
if i cant use the on board esc can someone reccomend a reversable ESC that can run this motor...its a 12turn 550 size up to 8.4v brushed.

im on a matek f722-wpx

thanks!