Flux capacitor override switch wire. Appears yours is non- functional. Be extremely careful t speeds over 88mph. But I will look at mine in the am and see what is really is .....
That looks to be a ground wire that attaches to the lower frame rail, drivers side near the evap line bracket. Trace the wire back to its origin, it should attach to the trans bolt near the starter.
I think OleJoeDad is right. I have one that looks about like that, except it's attached to the frame rail and pulled loose from the transmission. You can see one end bolted to the frame rail and the other end near the exhaust down pipe, in this pic.