What is overdrive on a truck?

Eaton Fuller RTO-The O means one over drive gear after the 1-1 ratio. RTOO means two gears after 1-1 ratio. My Eaton Fuller RTO 14613 is one over. 12 is direct and 13 is now considered over drive.

 

Not to be confused with "Georgia Overdrive".

 

Is that like "Mexican Overdrive"?

 

Bingo. Dave Dudley made the phrase "Georgia Overdrive" famous in "6 days on the road". I suppose you could insert any place with a long downhill run. Do they have hills in Mexico?

 

" Georgia Overdrive " That's the fuel saving gear right? LOL

 

Fuel savin', make up a little time, get past the "shake zone" gear.

 

700 r4 is a good tranny. Mine is 22 years old and never been opened up. *knock on wood*
Now I gotta look at the gear ratios and see what they are.

 

Overdrive means that the output of the transmission is turning faster than the input, so it is multiplying the drive shafts speed faster than the engine is actually going.
A typical top gear overdrive is 0.73 so if your engine is doing 1,400 rpm then your driveshaft will be doing 1,400/0.73= 1,917.8 rpm.
In a direct drive transmission they'll be both going 1,400 rpm
Yes a direct drive is more energy efficient at cruising speeds but requires a rear axle ratio (eg. 2.64) that is great on the highway, but not so good at getting you started on a hill, on soft soil with a real heavy duty load. An over drive uses a rear axle ratio that is great at getting started in tough conditions, but not so great at higher speeds (eg. 4.11). They are both compromises depending on what you are hauling and where the truck will be running. And there are a pile of combinations depending on tire sizes, speed you want to run at, engines optimal rpm, etc.

 

That was the predecessor to the 4L60 wasn't it?

 

It had to do with the driver, not the country.

Wasn't that a song by Wall of Voodoo? "I'm in mexican overdrive! I'm in Mexican world overdrive."