Just bought a 92 Explorer 4X4

I just bought a 92 Explorer and I'm having some trouble. I can't find a wiring diagram for putting in a new head unit for the sound sytem. I can get power to the unit, but I'm lost as far as the speaker wires go though. I have tried every combination I can come up with, but none of them work. Any suggestions?

Sup,
I learned this the same way your doing it, but I got some advice.
The factory speaker wire has two wires for each one the negative wire is the one that has a black line down it,there both going to be the same color though, All you have to do is figure out which wires are the rear speakers.

Unless your stereo is like mine and none of the speaker wires at the harness are the same color AND you pulled out a speaker to try and get some hints there only to find that those colors are completely different from any of the colors at the harness.

Anyway, I cut the thick grey wire that holds all the little speaker wires and then found out that I shouldn't have? Is there an amp somewhere in my '94 Explorer that I can take out and then replace all my wiring? This boy's quite frustrated...