 Ok lets see if i can help some
First for your overdrive. Pulling with overdrive ON, on FLAT ground is fine, with minor hills. Go ahead use it it wont hurt. If you hit hill not mountain, well those too, but just hills that the motor is gonna have to work a little, turn the sucker off, you'll burn something up. (experience talking) So just always be thinking easy to move od is good, have to work to move od off.
As for the trailer your way good at pulling that, shoudent have a problem at all.
Ok well that Blue wire is the brake wire for the trailer. So let me put this into comparison. Electronic brake controller, at store $100.00, 20 ft of blue wire $7.99 (high)
Profit of bussiness for something that can easily be done your self $125.00.
It pretty easy to install one of those brake controllers. there is a harness you can get that connect from the brake controller to the harness under the dash. then you run a wire thru the firewall to the back and plug it into the wiring connector. whallah brakes on trailer.
if you want to know more or let us know
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1984 Ford Mustang GT350 20th Anniversary Cobra
1991 Ford Explorer
1993 Ford F-150 300 I6 5 Speed
1999 Ford Taurus Wagon
"Don't Crush Them ... RESTORE THEM"
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