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Senior Charter Member
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Discussion Starter #1
I am curious about how the rear end gear swap works.....If I am understanding this correctly, a 3:73 gear would spin the back tires one turn for every 3.73 turns of the driveline? so higher gears give more power and less top end speed...? right?

Thanks!
 

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Senior Member
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Not more power, more RPM.

You have to figure the trans into the equation as well.
 

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FFCobra Fanatic
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The higher number, 3.73 vs. 2.73 for example, is referred to as a lower gear ratio. It will give you more torque at the rear wheels as well as requiring a higher engine RPM for a given road speed. You will usally get quicker acceleration using a lower gear. Hope this helps.
 

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Just to keep things straight, the motor produces the power whether in terms of horsepower or torque. Gearing does not produce torque or power. Gearing provides mechanical advantage.

Think of the gears on a 10 speed bike. If the front gear with the pedals attached has 40 teeth and is connected by a chain to a rear gear with forty teeth, you have no mechanical advantage. If the rear gear has 80 teeth, the front gear must turn twice for every revolution of the rear gear. To the rider working the pedals this mechanical advantage makes the pedals easier to pump. An advantage when going up a hill. The disadvantage is that the rider must pump the pedals twice as fast to achieve the same speed. Obviously, the opposite is true if the rear gear has 20 teeth.

Think of a car with no transmission but only a shaft linking the motor to the rear end. In this situation, we would have to determine how much power the motor makes and select a rear end gear which would allow the power of the motor to readily overcome inertia as well as propell the car uphill plus allow for the greatest maximum speed. The trade offs become obvious. The trannny's multiple gear selection offers a method to overcome these trade offs.

In addition, the tranny gears provide further mechanical advantages. First gear is not as fast as second but will accelerate quicker, second gear is not as fast as third but will accelerate quicker, etc..

Generally, the greater the power produced by the motor, the less steep the rear gear. For example, a 225 hp 5.0 is better paired with a 373 gear rear end than a 3.08. Some might even prefer the 410's with the stock 5.0. Many believe the 355's to be a good choice to go with the 5.0. My windsor produces 437 hp and the rears are 373's. For me this is a great combination; ample acceleration plus proper rpm for 100 mph cruising.

All the best,
Bob
 

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FFCobra Fanatic
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ive got 4.10s in my car w/ an aod w/3500 converter and im going to 3.73 gears. The trick is NOT to pass the powerband of the engine abality, for instance, you can actually slow a car down with a gear that is too big, blowing through 1st and 2nd gear too fast is NOT good, you need to use the powerband to its advantage, and the car will thank you....
 

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Originally posted by cobra9268:
you need to use the powerband to its advantage, and the car will thank you....
This is the reason, I maintain that a 3.27 rear with the special .8 OD t-5z is the Perfect combination.

you get a much longer first gear with the 3.27 and the lower first gear ration of the t-5z. You can run about 140 in fourth at about 6000 rpm and then you have 5th to cruise in.

Personally my car has 3.55 with the earlier t-5 with .67 OD. First is blindinly quick, the car runs out of speed at 120 in fourth and falls on its face in 5th.

Now if you have ENOUGH HP, Its gonna go, regardless of the ratios.

A comparison of the numbers. the first column is for the t5z with 3.27 the second column is my set up of older t5 with 3.55

1st gear/6000rpm ...47.2 .......... 38.3
4th gear/6000rpm ...139.2 ........ 128.2
5th gear/ 60 mph ...2068rpm ..... 1909rpm

Just my opinion of the PERFECT Settup. Opinions will vary.

[ August 28, 2002, 12:54 PM: Message edited by: CobraEarl ]
 
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