Differential speed sensor

Ordered a set of gears from ecgs, spoke with a gentleman and he asked if it had abs. Thought to myself "why does abs matter for gears?" Well I said no, cause I don't actually have abs. Turns out though, the speed sensor on the top of the diff is for anti lock, so the rear wheels don't lock up under brake pressure. Anyone running a truck without a rear sensor notice any rear wheel lockup under hard braking?
Before I throw in any of the diffs (new rebuilt, or factory) and waste the time, figure I check here first.

 

ABS is your anti-lock brake system. Rear wheel ABS was standard from 1990. And it only works in H2. There should be an ABS light on your dash.

 

There is no abs light on dash, with ignition on, there is a 'rear anti lock' light that illuminates. Does the anti lock not work in 4wd? I understand how abs works, but I could've sworn I had all 4 tires locked up right after I bought the truck and noticed there was no abs module.
Guess I'll just throw in the non abs housing and get the right gear ratio under the truck once and for all... I'm assuming the anti lock light will be on though after removal of sensor, so I'll look at diagrams to dummy that switch so light doesn't illuminate; or just remove that bulb from IP.

 

The rear anti-lock does not work in 4wd.