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Discussion Starter #1
i have a manual 6.0 xlt crew cab 8ft bed fx4 package and im having trouble finding out the any of the ratios..im new to diesel and finding it hard to research.
modifications: 4inch straight pipe, 31inch tires, bullydog tuner
 

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Most likely it's got 3.73 gears. Have you researched the numbers off the differential housings?
 

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Discussion Starter #3
i have not climbed under yet but i dont believe the final drive is 3.73 because my mustang has 3.73 and at 25 mph its at 900rpm but in the truck it is 750 but the final drive doesnt mean anything if you do not know the gear ratios. maybe 3.53s?
 

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Lol, why would you be in 6th while only traveling 25mph... Can't really compare a car to a truck when determining rear end gear ratios. (tire size makes a huge difference) With that being said, my tires are stock, final drive is .71, rear-end gears are 3.73 and at 70 mph motor is turning 2000 rpms.
 

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Easiest, fastest, most accurate way is to look on the differential!
 

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jack it up and spin the tire 1 revolution. Count how many time the driveshaft goes around. 3&3/4 would be 3.73's, a little more than 4 would be 4.10's, 4.5 is 4.56's etc. Pretty basic.
 

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The ratios that you are looking for are all over the interweb, you just need the pn codes.

That being said, the low range ratio will be on the id plate on your transfer case. get under there with a wire brush and start looking. The diff tag will need to come off because the bolt covers the first number. If it says 3 73 (with a space between the 3 & 7) it's an open diff. 3L73 will be a Trac-Loc diff.

How good are your math skills? Because you have a manual, once you determine your rear gear, you can determine the transmission gears with this:
Gear ratio = (rpm x tire diameter) / (mph x 336)
gear ratio = (2000 x 31.5) / (70 x 336)
gear ratio = 63000 / 23520
ger ratio = 2.678

We know that there is a 3.73 r&p 2.678/3.73=0.717xxx, now we know the OD drive ratio that was mentioned earlier.

Just remember to divide that answer by your rear end ratio to find your transmission ratio. This doesn't work so well with an automatic unless you can determine how much slip is in your converter.


http://www.offroaders.com/info/tech-corner/reading/mph-rpm.htm
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ZF6 gear ratios...
1st Gear:
5.79
2nd Gear:
3.31
3rd Gear:
2.10
4th Gear:
1.31
5th Gear:
1.00
6th Gear:
0.72
Rev Gear:
5.23
 

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Discussion Starter #12
The ratios that you are looking for are all over the interweb, you just need the pn codes.

That being said, the low range ratio will be on the id plate on your transfer case. get under there with a wire brush and start looking. The diff tag will need to come off because the bolt covers the first number. If it says 3 73 (with a space between the 3 & 7) it's an open diff. 3L73 will be a Trac-Loc diff.

How good are your math skills? Because you have a manual, once you determine your rear gear, you can determine the transmission gears with this:
Gear ratio = (rpm x tire diameter) / (mph x 336)
gear ratio = (2000 x 31.5) / (70 x 336)
gear ratio = 63000 / 23520
ger ratio = 2.678

We know that there is a 3.73 r&p 2.678/3.73=0.717xxx, now we know the OD drive ratio that was mentioned earlier.

Just remember to divide that answer by your rear end ratio to find your transmission ratio. This doesn't work so well with an automatic unless you can determine how much slip is in your converter.


Tires, Gears, MPH and RPM Relationship Between
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the most amazing math i will ever use in my life
 

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Man, you do some beautiful machine work Rich!
 

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What is the thread size on those? I could use a shifter knob on my 67 F100... It's got a T18 trans.
 

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What is the thread size on those? I could use a shifter knob on my 67 F100... It's got a T18 trans.
The ZF5 and ZF6 don't have threads, the shifter rod has splines and the factory knob is press/glued on.

The only way to use a aftermarket knob is to weld on a threaded rod to accept the aftermarket knob, or find a aftermarket knob that uses set screws. I make them with a set screw.




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