Gear vendors OD

I run one in my 67 Dart with 27" tire, 4.10 gear. 2800 rpm @75mph highway cruise. If you are not in the flow of traffic in FL you are asking for trouble. Gear reduction in O/D is .78 I only use a shifter mounted switch and a relay to manually control the O/D. A slight throttle bump when disengaging allows O/D to disengage smoothly. I've run 1/8 mile in 2nd over vs normal 3rd and the car picks up 1.5 mph. 1/4 mile I do not use it at all. I bought mine used and glad I did since round trip is 100 miles to run at the nearest track.