373 rear gears worth doing?
02-17-2009, 08:35 PM
#12
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02-18-2009, 06:35 AM
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02-18-2009, 08:28 AM
#16
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I don't know why your mechanic would say that. Conventional wisdom is that 3.73 are best for supercharged car. But that conventional wisdom is base upon quarter mile racing. Most supercharged cars with 4.10s run out of gear (redline in fourth) before they reach the finish line. Dedicated racers solve this problem by going to a taller tire.
A lower gear is a torque multiplier and it gets the motor into it peak horsepower faster. Especially with centrifical superchargers. But, this comes with a cost.
3.73s will have a 14% higher rpm than stock gears at any give speed. 4.10s a 25% higher rpm. In town these differences are minor because all you do is just drive in the next higher gear so there is very little impact on gas mileage.
A lot of people say 4.10s are no big deal on the highway at 65 mph. Stock rpm in fifth would be somewhere around 1940, 3.73s would be around 2210, and 4.10s would be around 2430. A lot of people don't mind driving at near 2400 rpm down the highway.
On the interstate most people will drive 75-80 mph. At 75 with stock gears the tach reads around 2240. With 3.73s it should read around 2550 and with 4.10 it should read around 2800. At 80 mph is around 3000 rpms. There is a definite gas mileage impact if you do a lot of instate driving.
A lower gear is a torque multiplier and it gets the motor into it peak horsepower faster. Especially with centrifical superchargers. But, this comes with a cost.
3.73s will have a 14% higher rpm than stock gears at any give speed. 4.10s a 25% higher rpm. In town these differences are minor because all you do is just drive in the next higher gear so there is very little impact on gas mileage.
A lot of people say 4.10s are no big deal on the highway at 65 mph. Stock rpm in fifth would be somewhere around 1940, 3.73s would be around 2210, and 4.10s would be around 2430. A lot of people don't mind driving at near 2400 rpm down the highway.
On the interstate most people will drive 75-80 mph. At 75 with stock gears the tach reads around 2240. With 3.73s it should read around 2550 and with 4.10 it should read around 2800. At 80 mph is around 3000 rpms. There is a definite gas mileage impact if you do a lot of instate driving.
02-18-2009, 08:42 AM
#17
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Well what my mechanic was getting at and what I am asking, is whether or not there is a big enough gain going from stock ratio to 3:73s' to justify the install costs. He has alot of race and performance experience mostly with Ford and Mustangs, He feels that if I go FI gears are not needed, and actually will push me through the rpms too quickly and will hurt boost in the mid-range. Granted you are correct that if you are definitely doing gears that 373 is the way to go when FI, but are they needed?
Well what my mechanic was getting at and what I am asking, is whether or not there is a big enough gain going from stock ratio to 3:73s' to justify the install costs. He has alot of race and performance experience mostly with Ford and Mustangs, He feels that if I go FI gears are not needed, and actually will push me through the rpms too quickly and will hurt boost in the mid-range. Granted you are correct that if you are definitely doing gears that 373 is the way to go when FI, but are they needed?
Last edited by Armydad; 02-18-2009 at 08:46 AM.
02-18-2009, 09:32 AM
#18
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depend on what kinda sc'er you have and what kinda of racing you do and what tire you run 4.10's are good for like a vortech that doesnt make boost right away i tihnk but with a kenne bell 3.73 or 327 is fine
02-18-2009, 10:46 AM
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This was in modernmustangs help section for rear ends:
4) Which gears should I get?
Most people opt for 3.55's, 3.73's, or 4.10's. 3.55's will give some increase in performance without much of a hit on top-speed or fuel economy. 3.73's are a good midrange gear set. They give you a nice quick start and have a decent top end for everyday driving. For drag strip racing you'd probably want 4.10's, although race gearing can be affected by several other factors such as vehicle weight, rpm's, and rear tire nTireDiameter.
If you are equipped with a supercharger, 3.73's and 4.10's may be too much gear, so you may want to opt for 3.55's or stick with the stock gears
4) Which gears should I get?
Most people opt for 3.55's, 3.73's, or 4.10's. 3.55's will give some increase in performance without much of a hit on top-speed or fuel economy. 3.73's are a good midrange gear set. They give you a nice quick start and have a decent top end for everyday driving. For drag strip racing you'd probably want 4.10's, although race gearing can be affected by several other factors such as vehicle weight, rpm's, and rear tire nTireDiameter.
If you are equipped with a supercharger, 3.73's and 4.10's may be too much gear, so you may want to opt for 3.55's or stick with the stock gears
