was changing master cylinder on lumina and had to remove black box that was mounted to it i assume it is abs control, it was geared and when i removed it the gears had tension and spun, i should have stopped when i saw that i had to remove the box but didnt, what do i have to do when putting it back on,any help would be appreciated,

 

get one from the wreckers and replace it as a unit

 

you mean the black thing attached to the master cylinder on the firewall? If so thats a brake booster. I dont think there is a seperate comp for ABS just sensors, and controlled by BCM.

 

I dont know what you are reffering to when you say the "BCM" but on every ABS equipped vehicle the abs system has its own computer.