Thread: Some contemplations on overdrive

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It's one of those things that would be interesting to see the real world numbers comparison on a dyno. Maybe the difference would be minute.
According to my calculations your 4.11 with a .62 overdrive would produce the same total ratio in top gear as a 1:1 tranny top gear and a 2.54 rear end.

Originally Posted by willowbilly3

It's one of those things that would be interesting to see the real world numbers comparison on a dyno. Maybe the difference would be minute.
According to my calculations your 4.11 with a .62 overdrive would produce the same total ratio in top gear as a 1:1 tranny top gear and a 2.54 rear end.

That would be correct, but with a 2.97:1 low gear and a 4.11:1 rear gear, it launches quite well!!!! The lowest ratio low gear I know of in a stock box 4 speed would be a 2.20:1..... When you figure the ratio in low gear, then it becomes evident which rear gear will give the hardest launch and quickest 60 ft. time......a four speed with a 2.20 low gear, 1:1 top gear and a 2.54 rear gear will not launch near as hard as a 5 speed with a 2.97:1 low gear, 1:1 fourth gear, .62 overdrive 5th gear, and a 4.11:1 rear gear....(and we won't even talk about how much fun the five speed is with a 6.00:1 rear gear!!!!)

Originally Posted by Dave Severson

That would be correct, but with a 2.97:1 low gear and a 4.11:1 rear gear, it launches quite well!!!! The lowest ratio low gear I know of in a stock box 4 speed would be a 2.20:1..... When you figure the ratio in low gear, then it becomes evident which rear gear will give the hardest launch and quickest 60 ft. time......a four speed with a 2.20 low gear, 1:1 top gear and a 2.54 rear gear will not launch near as hard as a 5 speed with a 2.97:1 low gear, 1:1 fourth gear, .62 overdrive 5th gear, and a 4.11:1 rear gear....(and we won't even talk about how much fun the five speed is with a 6.00:1 rear gear!!!!)

Well, my whole idea was whether a 1:1 top gear had less drag than an overdrive, or would transmit power more efficiently. To me it just seems like it would. I made an effort to try and explain it was a theoretical postulation but many people have responded with how the lower gears would now be all wrong. If you read the original thread I had made my best attempt to negate that by stating that in my theoretical transmission every gear would have the same overall ratio as it's overdrive counterpart, that is the same engine rpm to tire rpm in every comparable gear, so the launch would be the same. Maybe I need to take one of those Art Carney courses so people can understand me better. I don't know any other way to explain it any better.