At 45 mph there is little difference in fuel economy between direct drive and overdrive. One factor may be that when the A/C clutch is disengaged you will see a higher mpg display. When operating in a lower gear, the A/C will cycle more frequently.
I remember cars equipped with the Borg Warner automatic overdrive from the mid 1930s through the 1960s. The overdrive was engaged by releasing the accelerator at a speed of 28 mph or higher. I often wondered why manufacturers chose the Borg Warner overdrive as opposed to a 4th gear in the manual transmission that was higher than direct drive. My guess is that the Borg Warner unit was used so that motorists would not lug the engine as they might if the overdrive was the top gear in the transmission.
1 Like
I seem to faintly remember that our 54 ford had the overdrive in it. I donāt remember anyone actually using it though, but that was a long time ago and I was probably riding in the back window.
1 Like
The Willys Overland, the Jeep all metal Jeep station wagon that came on the market in 1946, had the 4 cylinder Go Devil engine used in the military Jeeps. The Borg Warner overdrive was standard equipment in the Willys Overland. I suppose the reason was so that the engine wouldnāt be over revved at highway speeds.