I am well aware of what overdrive means, and I'm also well aware of the heat losses when using overdrive gear ratios. Those losses are the direct reason for the current direct-drive transmission fad, trying to squeeze every drop of fuel you can out of a drivetrain. Those losses are minimal, at worst a couple percentage points. Bruce made it sound like running an overdrive was just chopping your horsepower in half! Frankly from the driver's seat you would be hard-pressed to tell the difference between a direct drive setup and an overdrive setup, as the overall gearing from flywheel to wheel end is basically equivalent.
The origin of double over goes back to the twin stick days, when the big steppers had both Transmissions turned around, hence double Overdrive. As I just pointed out a post or two ago, the first single stick double over had three overdrive ratios,yet was called specifically the 13 double over.
And if I had to Hazard a guess, the most egregious misuse of double over, using it to describe a single overdrive transmission, most likely started as a genital measuring contest at the lunch counter.
Gear Ratios: Misinformation at its worst.
Discussion in 'Experienced Truckers' Advice' started by Hammer166, Apr 28, 2021.
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You guys are splitting frog hairs.
Just like a guy jumping on me for calling Lo in a RTLO 1st gear.
Its first gear in the box. 1-5, or Lo-4 on shift label.
On a consumer point input shaft is turning same speed as engine. A rtlo has 2 overdrive ratios to be used coming out of the tail shaft. In theory yes it has a single overdrive gear in main box of a married transmission. 2 overdrives in separate divorced boxes accomplish the samething.
Most guys don't have a simple clue how any of it works. Zero point in getting worked up about it.Brettj3876 and PoleCrusher Thank this. -
IMO overdrive is the ratio between the crank and driveshaft. IOW the driveshaft is ''overdriven''.
I guess from Bruce's perspective 20% over drive is double10% overdrive.
I don't think anybody is getting worked up, We are just ''bench racing''. -
Everyone communicates different.
Bruce should have said "2 overdrive final ratios".Bean Jr. Thanks this. -
Almost Every driver on this site has driven a truck that when loaded to max on a hard pull you might be in 5 hi or lo .. put 2.64 in the back and now you’re in and out of the basement gears. Only way around that is to turn up power a bunch. A direct drive transmission has different ratios in it so it’s not a big issue .
Hammer166 Thanks this. -
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Bean Jr., Dale thompson and Cat sdp Thank this.
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Oh I agree. They are direct, or overdrive.Bean Jr., PoleCrusher and Hammer166 Thank this. -
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