Mitsubishi Montero Limited (not Sport) 2001, 130,000 miles- Upon changing my hub assembly for the second time to solve a whirring noise and constant subtle vibration, the mechanic had to air-chisel the hub assembly from the bolt heads to get the rusted hub to break free and slide-hammer out. He knocked out a tooth in the sprocket behind it which I assume is my ABS trigger since the tubular ABS sensor comes right up to it. The sensor is clean. Now my ABS pump self-actuates (sputtering) randomly- but frequently- while driving and/or braking on the same side as the missing gear tooth. The mechanic claims missing " only one tooth" wouldn't cause this and I need a new ABS computer! What is the sprocket piece called (and is it part of something larger like the axle) and how hard is it to change since the Hub was such a pain to remove? I am competant enough to change brakes, calipers & rotors, but haven't gone further in yet for lack of tools. Many thanks!