I have a 98 Tahoe 2wd, my front AC works fine, but rear AC doesnt cool at all, my question is there a seperate AC compressor for the Rear AC, if so where exactly is it to see if needs a freon recharge. Any help will really help my back seat passengers, for the heat here is South Texas is unbearable.

Sounds like you may be low on freon, only one compressor used here, have the pressures tested this will tell you if it is low, then of course there may be a leak.