What axle ratio is best for acceleration?

[jaybyrd]

Would a 4.10 LS be the best for acceleration on a 2000?
Would lower gear ratio's then be better for applying torque.

Just wondering why there are different ratios offered.

 

[Webster3]

Stock tires and rims?

 

[DocVijay]

DIfferent gears are offered for different size tires, and also for towing. A higher number (3.73 vs. 4.10) gives a lower overall gear ratio. A bigger number gear would give faster acceleration, but is offset by having much lower top speed. So a 4.88 gear would give you quicker acceleration, but your engine would be screaming along at some really high RPM on the highway. There are always tradeoffs.

I switched form a 3.73 to a 4.10 to offset he increase in tire size when I got my 33's. My overall acceleration won't really go up as it's canceled out by the larger tire circumference. If oyu don't change the tire size, having higher gears will quicken it some. Just don't go too high (low).

Also, the limited slip doesn't really affect the gear ratio at all, it just helps to get the power to the ground. It will only help acceleration if you have an open diff and spin a tire when you take off. An LS will help to get more power to the ground rather than tunring rubber to smoke.

Hope that helps.

 

[Robert]

Go and ride a 10-speed bicycle. First start off in the lowest gear (1st - duh!) and feel how easy it is to take off. Now try seeing how fast you can go (you'll probably top out at about 5 MPH before your legs look like a hamster in a running wheel). Next, come to a stop and put it in its highest gear (10th - again duh if it's a 10-speed). Now try taking off. Feel how hard your legs have to work to get the bike moving?

That is what happens to your motor with high gears versus low gears. Your motor has to work harder to get moving with a numerically lower ratio however if you go too much in the opposite direction your motor will quickly run out of breath. You want a good balance of acceleration and highway performance/comfort/fuel economy. There are several different diameters of tires offered on the Explorer. Tire diameter affects overall ratio. When Ford installs a taller diameter tire, they install a lower axle ratio to make up the difference. For instance an Explorer with 28" tires would likely come with a 3.08 or a 3.55 ratio whereas the 30" tires came with a 4.10 until the last couple of years when Ford started including 3.73s with the 30" tires.

 

[SteveVB]

What they said...

but remember you need to consider everything from the engine power band, the transmission ratio, the rear ratio, and the tire diameter. You have to consider the axle as part of a system. Its a whole system, that said, a lower rear gear will provide greater off the line push, but may not make you any faster if the engine doesn't have the power in the right rpm range. In a stock vehicle with offerings of multiple gear ratios the lower geared vehicle should have better off the line performance.

Consider this: the 4r70W has a 2.84 first gear, and the A4LD (both transmissions) has a 2.46 first gear if they both are installed in a vehicle with a 3.55 rear the first gear gearing is quite different - 10:1 for the 4R70, and 8.7:1 for the A4LD, to match the gearing of the 4R70 the rear in the A4ld vehicle would have to be lowered to around 4.10s to get the same gear reduction. One part of the system.

If you "Mod" your engine with cams, filters etc and raise the rpms at which you create power you will need more gear to get into your power range. A stock vehicle with 3.55s and some mods, may have more power at 300-400 rpm higher, so a switch to some 3.73s can get the engines power to the ground. A stock vehicle offered with different engines in the same chassis make power in different rpm ranges , manufacturers use the rear axle to "even" out the drive train.

Just some things to think about