1983 Suburban what is this wire?

[1983 Idaho Suburban]

I just got my first Suburban so dont know what this is but the rubber insulation is melted and under that looks like pilly cable? Its jump from the middle of the transmission to the rear transmission but it lays on the brake drum and the part that touches the em brake drum is burnt?
I may have called every thing by the wrong name sorry not a mechanic!