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I'm confused about gear calculations now....

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Old 02-07-2008, 12:37 AM
  #1  
ripped camel
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Default I'm confused about gear calculations now....

I was reading a few threads and am confused about gear calculations. Correct me if I'm wrong......

When figuring what type of gears you have you're supposed to use 5th gear right?



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Old 02-07-2008, 01:00 AM
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dsbsurfn
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Default RE: I'm confused about gear calculations now....

If you are trying to find out the gear ratio in your rear, do it in neutral.

Mark the wheel and the driveshaft. Make one full revolution with the wheel while counting how many times the driveshaft spins. If the driveshaft spins ~ 3 1/4 turns then you have 3.27 gears. Just over 4 turns would be 4.10 gears.


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Old 02-07-2008, 01:06 AM
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ripped camel
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Default RE: I'm confused about gear calculations now....

I'll try that if I can get it on a lift.

I see people always saying things like " @ 70 my rpms are at 2100" are people talking about being in 5th or 4th when they say that?
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Old 02-07-2008, 01:56 AM
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ZW99GT
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Default RE: I'm confused about gear calculations now....

5th. But you don't need a lift to do the tire/dshaft thing. Just jack it up and watch. It's really simple.
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Old 02-07-2008, 02:38 AM
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vertmustang98gt
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Default RE: I'm confused about gear calculations now....

Thats is a 3.27 gear, and it is pretty easy to find your gear ratio on the internet just find a website that gives all the boxes and fill it in for the gear ratios for your tranny. That is how I found out wat I had in my car stock and what 4.10's would be @ 70. It was exactly right too . So you can trust it, richmond as a good calculator on their site.

ORIGINAL: ripped camel

I'll try that if I can get it on a lift.

I see people always saying things like " @ 70 my rpms are at 2100" are people talking about being in 5th or 4th when they say that?
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Old 02-07-2008, 09:53 AM
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Default RE: I'm confused about gear calculations now....

ORIGINAL: ripped camel

I'll try that if I can get it on a lift.

I see people always saying things like " @ 70 my rpms are at 2100" are people talking about being in 5th or 4th when they say that?
if you've got a 5 speed, put it in 5th gear and get up to 70 mph:

3.27 ~ 2100 rpm
3.73 ~ 2300 rpm
4.10 ~ 2500 rpm

unless your tach is off, you should be able to tell which gears you have. or you can jack the rear end up and turn the driveshaft and count the number of revolutions to make the tires turn 1 revolution, either way will work.
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Old 02-07-2008, 10:27 AM
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ripped camel
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Default RE: I'm confused about gear calculations now....

Okay, that's what I thought. I just read in a few different threads now people saying to put it in 4th when figuring out what gears you have. I always thought it was 5th. So after reading multiple people saying that I thought maybe I've been wrong all along.

Thanks for the clarification guys.
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Old 02-07-2008, 02:06 PM
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Default RE: I'm confused about gear calculations now....

ORIGINAL: ripped camel

Okay, that's what I thought. I just read in a few different threads now people saying to put it in 4th when figuring out what gears you have. I always thought it was 5th. So after reading multiple people saying that I thought maybe I've been wrong all along.

Thanks for the clarification guys.
The reason a lot of people use fourth, is because its 1:1. its easier to do the math.
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Old 02-07-2008, 02:23 PM
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angcobra
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Default RE: I'm confused about gear calculations now....

The other factor when using speed and RPM is the tire size, different size tires will change the speed/RPM relationship.

Go with the turn 1 wheel and count drive shaft rotation.
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Old 02-07-2008, 02:26 PM
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tbirdscwd
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Default RE: I'm confused about gear calculations now....

Yeah, your tires can throw it off quite a bit if they are different from stock tire height.
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