Mystery wire

[87TIGN]

I have about an 8 guage red wire stranded running from the positive battery cable and it is long enough to make it around the firewall and to the driver side of the tranny and I am about to drop my motor in and forget what it is for.... Can anyone help me?
-Andrew

 

[STGMAN]

It goes under the harmonic balancer then up to the back of the alternator.