abs problem with new hubs

[60ratrod]

ok so i replaced both of my front hubs on my 01 tahoe since they were making humming noises. but now my abs does one of two things, its over active when braking and slowing down at 20mph and slower with the light off, or its inactive and i have normal brakes at all speeds with the abs light on. this all started when i replaced the driver's hub. since it started there i replaced the new speed sensor with the old sensor off the old hub since i knew it was good. no change. i did inspect the reluctor ring on the inside of the new hub for any damaged teeth and there are none. but i did notice a couple things. the first is the old hub is packed full of grease where as the new one doesn't have much on the inside. is this or will this be an issue down the road? also, there was what looked like shims on the new hub under where the sensor bolts to the hub. could this also be an issue? i reinstalled the shims when i swapped in the old sensor since they came with the new hub, even though there weren't any shims on the old hub. i think my first course of action with this will be to remove the shims and take a piece of wire and measure the distance from the top of the teeth on the reluctor to the mating surface of the sensor and compare the old against the new. or is there something else that i should be doing?