Diff Gears

[LNYMRKO]

Can someone please explain them to me ? I'm having trouble understanding what the ratios mean, eg 4.3s, 3.9s, 4.11s, etc. What's the difference in acceleration/top end ? Etc.

Thanks.

[[RX2]]

ask me on the phone next time, coz i cant be fuct xplaining in writing.

[zeroyon]

here's an attempt at a simple POV on it.

Well in a 4.11 for each 4.11 turns of the tailshaft the rear wheels will turn once.

and a 3.55 the tail shaft only has to turn 3.55 times to get 1 rotation out of the wheel.

this makes the 4.11 a lighter load on the engine and makes teh car accellerate faster.

The 3.55 has a heavy load on the car but is capable of rotating the wheel more total times for the same RPM. thus giving you a greater top speed.

Hope i got that the right way round :)

[v8souproar]

butters is exactly correct.

Just to confuse ya LNYMRKO, if i was to go from a 3.45 to a 4.11, i am going to a lower diff ratio.

[[RX2]]

higher the number : 5.2 : 1 , = faster accell , = less top end speed......
lower the no. : 3.08 : 1 , = slower accell, = more top end speed.

[LNYMRKO]

Cheers guys.

[Sketch]

Theres more too it also,, you can think about performance from a numbers point of view.

Depending on gearbox, and overdrive config, you have a final drive ratio + gear tourque multiplication relative to the engine crankshaft.

For a vehicle to be a strong street performer, you need a torque multiplication ratio of at least 9:1. To figure this, multiply the transmission's first gear ratio by the rear end's ratio. 9:1 is the MINIMUM "threshold" value, excluding any other factors, to be a strong street performer.

Naturally, a "steeper" ratio "higher than 9.1 (up to a point) will enhance performance even further, while increasing RPM rpm at any given speed, decreasing sreetability.

Example:
A C4 has a first gear ratio of 2.46:1. Assuming you have a rear end ratio of 3.70:1, the equation would be: 2.46 X 3.70 = 9.102.

So get the drive ratio of your gearbox in first gear, and that of your diff ratio. and follow this formula.
it will be interesting to see what results you all get.

IN the Xy, with 2.7's i get a performance ratio of 6,77, not bringing it into teh performance class :) but still running a 14.1,

after next week, with the 3.9's and 2500 stall converter, taht changes the factor to 9,62, giving me low 13's and a solid performance factor,, but more fuel consumtion..

what do you guys get?