At 06:28 PM 5/23/00 -0500, you wrote:
>how do the rear gears relate to power output at the wheels?
In addition to changing the direction of power flow by 90 degrees
(driveshaft to axles), changing rearend gears alters the torque
delivered by the engine and transimission. Assume that the engine
and tranny are delivering 100 lb-ft of torque just for an example.
Everything else being equal (STRESSED), a 3.92 rear end puts
392 lb-ft of torque to the ground ... a 4.10 puts 410 torque to
the ground.
>will a lower gear (as in 3.9 is lower than 4.1) ratio give you better
gas mileage?
Actually, 3.9x is a higher gear than a 4.1x in the auto industry.
Just need to remember 'higher the number = lower the gear'.
Because the engine needs to work more to go the same distance
(4.1 turns of driveshaft vs 3.9 turns of driveshaft to turn
rear wheels one complete revolution), you normally get less gas
mileage with a 4.1 rear end than a 3.9 rear end.
>how do they affect top speed/0-60 speed?
Because of the torque multiplication and the amount of power
band left in the engine, your 0 - 60' speed will be higher.
Because the engine with a 4.1 rear end gets out of its power
band before one with a 3.9 rear end, top speed with a 4.1
rear end will be less than one with the 3.9 rear end ...
everything else being equal (STRESSED).
There's a great article "All About Axle Gears" by David Freiburger
that appeared in Car Craft about a year or so ago that has as
good as an explanation of rear ends as I've seen.
Hope this helps.
Bob
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