I was wondering if anybody could explain the meaning of the numbers for the rear differential. (3.42, 3.73, 4.10.....) I understand gear ratios, but they are usually explained as something like 3:1 but what do those numbers mean. Are we supposed to just assume they are talking about like 3.42:1 or what?!?!

David S

 

Yes...they're to be considered as 3.42:1 , 3.73:1 , etc. It's just easier to type the first part... If you want a little toy, there's a table at http://www.f-body.org/gears/ with a whole bunch of presets to select from so you can see the RPM:MPH table.

 

/\ /\ /\ very cool link!! I read through and then read about "How Automatic Transmissions Work".........very informative!

Anyway, back to the original question:

Basically, a 3.42:1 ratio or a 2.73:1 ratio means that the driveshaft turns 3.42 times, or 2.73 times (or whatever the ratio # is) for every 1 turn of the rear axles. The lower the number (ie: 2.xx vs 3.xx or 4.xx) the "higher" the ratio is, and vice-versa, where a high numerical ratio is actually a "lower" ratio. A low ratio gear (such as 4.10:1 gears) means that the driveshaft --- and consequently the engine as well --- must be turning at a higher speed (or at higher RPM's) to get the same amount of speed or turns out of the axles, but it will help to increase the the mechanical advantage of the gears, and make it easier for the engine to turn the axles, which means quicker and easier overall to get the car moving.

Hope that helps ya!

 

Thanks a lot Capn Pete. That explained it for me. I figured the first number 3.42 was the drive shaft but i wasn't sure about what the :1 was. I was thinking about the ring and pinion too. Thanks again!

David S

 

Heres another article that sheds some light on the subject
http://www.carcraft.com/techarticles/1007/index.html