Gears & Specs
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Gears & Specs
Just looking for some clarification. When the gear ratio is changed, does it change the HP & Torque Specs by the percentage of change. I have a 2000 F250 V10 4.30. The specs say it has 310hp & 425ft/lbs, is this with the 3.73's? If it is than do I actually have 15% more HP & Torque. Or as I'm thinking, just my HP at the rear wheels is differant, the engine puts out the same no matter what. This question has probably been asked before, just can't track it down.
2000 F250 V10 Lariat 2wd 4.30 CC SB
2000 F250 V10 Lariat 2wd 4.30 CC SB
Post Fiend
Joined: Mar 2007
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From: Texas
I'm not an expert, but I don't think it changes your numbers. It just changes the power graph at the rear wheels in relation to the RPM. You'll realize more power at a lower RPM, but you'll top out quicker too. The whole key is to operate under your conditions in the ideal power range.
FTE Leadership Emeritus
Joined: Sep 2000
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From: Stephensville WI
The engine puts out 310 HP and 425 ft/lbs regardless of the gearing.
What you are chaning with the gear change is the torque multiplication to the rear wheels. This is a different measurement than the horsepower and torque output of the engine. You're multiplying the torque output.
For example, say your engine is producing max torque, 425 lb/ft. You are in first gear, which is 2.71:1. You had a 3.73:1 differential. 425 x 2.71 x 3.73 = 4296 lb/ft of torque at the rear wheels. Changing the differential to 4.30 makes 4952 ft.lbs. While that may seem like a small change, let's look at high gear. 425 x .71 x 3.73 = 1125.5 ft/lbs at the rear wheels. Changing to the 4.30 gearing increases the torque to 1297.5 ft/lbs.
What you are chaning with the gear change is the torque multiplication to the rear wheels. This is a different measurement than the horsepower and torque output of the engine. You're multiplying the torque output.
For example, say your engine is producing max torque, 425 lb/ft. You are in first gear, which is 2.71:1. You had a 3.73:1 differential. 425 x 2.71 x 3.73 = 4296 lb/ft of torque at the rear wheels. Changing the differential to 4.30 makes 4952 ft.lbs. While that may seem like a small change, let's look at high gear. 425 x .71 x 3.73 = 1125.5 ft/lbs at the rear wheels. Changing to the 4.30 gearing increases the torque to 1297.5 ft/lbs.
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Joined: Dec 2006
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think of it this way the hp and torque ratings are for the engine they change by changing parts of or on the engine.
the transmission and differential gears use that torque to appy varying force to the wheels. a higher ratio of gears in the differential ex. going from 3.73-4.10 will increase the force or torque at the rear wheels (while decreasing top speed) but will not change the hp/ torque ratings of the motor.
so if you change your gears you could feel more torque at the rear wheels than before, but it wont change that the motor puts out the stated hp and torque figures.
just thought i would add that as far as changing gearing goes when you go to a higher ratio like i was talkin bout it increases the torque at the wheels ie off the line power and power pulling like towing (mostly noticible just from a stop or in lower gears because the tranny will downshift to compensate when you are moving), but it will also require the motor to spin faster so you will be spining at a higher RPM to go the same speed in the same gear.
basically it is like driving in 1st vs 2nd and 2nd vs 3rd so on and so on therefore giving you more pull but higher rpms, it wont be THAT drastic but that the general idea
the transmission and differential gears use that torque to appy varying force to the wheels. a higher ratio of gears in the differential ex. going from 3.73-4.10 will increase the force or torque at the rear wheels (while decreasing top speed) but will not change the hp/ torque ratings of the motor.
so if you change your gears you could feel more torque at the rear wheels than before, but it wont change that the motor puts out the stated hp and torque figures.
just thought i would add that as far as changing gearing goes when you go to a higher ratio like i was talkin bout it increases the torque at the wheels ie off the line power and power pulling like towing (mostly noticible just from a stop or in lower gears because the tranny will downshift to compensate when you are moving), but it will also require the motor to spin faster so you will be spining at a higher RPM to go the same speed in the same gear.
basically it is like driving in 1st vs 2nd and 2nd vs 3rd so on and so on therefore giving you more pull but higher rpms, it wont be THAT drastic but that the general idea
Elder User
Joined: Apr 2006
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From: Edmonton, AB
Your HP at the rear wheels equals the Hp at the engine minus the losses through the drivetrain. The torque number is multiplied by transmission ratio and rear ratio as the others have stated. This assumes no slip in the trans.
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FTE Leadership Emeritus
Joined: Sep 2000
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From: Stephensville WI
Torque is a measurement of raw lifting or pulling ability. Horsepower is a measurement of work, or ability AND time.
Look at it this way; You have two guys working for you, loading bricks into trucks.
The first guy, Fred, carried 20 bricks at a time. The second guy, Gary, carrys 10 bricks at a time. Fred has more torque than Gary, he can move a bigger load.
Fred loads 20 bricks a minute. Gary loads 30 bricks a minute. Gary has more horsepower than Fred, he can do more work in a period of time.
Translate this to your truck. You changed the gearing, which means more torque to the ground, which means you can pull more, but this is happening at a slower speed (because you changed the gearing), so your rear wheel horsepower should be the same.
Look at it this way; You have two guys working for you, loading bricks into trucks.
The first guy, Fred, carried 20 bricks at a time. The second guy, Gary, carrys 10 bricks at a time. Fred has more torque than Gary, he can move a bigger load.
Fred loads 20 bricks a minute. Gary loads 30 bricks a minute. Gary has more horsepower than Fred, he can do more work in a period of time.
Translate this to your truck. You changed the gearing, which means more torque to the ground, which means you can pull more, but this is happening at a slower speed (because you changed the gearing), so your rear wheel horsepower should be the same.
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Be sure to thank him with some reputation points. If you go to his post in the top right corner you will see #8 then a picture of a scale and a red triangle. Click on the scale in the middle and a box will pop up where you can check I agree and a box to say thanks. This let's others know how helpful he is.
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Hi everyone My name is Joe I have 2005 SC V-10 Larait srw 4x4 I am trying to find out if there is a better way to get some gas mileage. I get 7 around town, and I am looking to keep this truck but can not afford 100. every two days Help will listen to any ideas
FTE Leadership Emeritus
Joined: Sep 2000
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From: Stephensville WI
Originally Posted by Joefine1
Hi everyone My name is Joe I have 2005 SC V-10 Larait srw 4x4 I am trying to find out if there is a better way to get some gas mileage. I get 7 around town, and I am looking to keep this truck but can not afford 100. every two days Help will listen to any ideas
Welcome to FTE, Joe. You'll get a better respone by starting a new thread, but the short answer to your question is "not really".
The best thing you can do for fuel economy is modify your driving style, keep your engine in tune and make sure your tires are inflated properly.
When driving, practice not letting the RPMs go above 2000. It is difficult, but it can be done. It takes a very very light foot.