What is my gear ratio
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What is my gear ratio
I recently pruchased a 2005 f150 xl supercab 4x4 with the 5.4 engine and a full 8ft box. I would like to know my rear end gear ratio but I can't make heads or tails of the codes on the door jams or on the rear end. If anyone could help me out I would greatly appreciate it. What numbers should I be looking for to translate into the ratio.
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Jack up your truck and get the rear wheels off the ground, and on jack stands. Put the vehicle in gear (engine off!)
Make a chalk mark on the driveshaft at 6 o'clock or another position you'll be able to easily identify when it gets back to that point. If you're looking from the side, 3 or 4:00 position may be better.
Make a note of a specific mark on the tire and it's position.
Looking from the passenger side, rotate the tire one full turn, and count the number of times the driveshaft spins to one revolution of the tire.
The result is your rear end gear ratio.
Make a chalk mark on the driveshaft at 6 o'clock or another position you'll be able to easily identify when it gets back to that point. If you're looking from the side, 3 or 4:00 position may be better.
Make a note of a specific mark on the tire and it's position.
Looking from the passenger side, rotate the tire one full turn, and count the number of times the driveshaft spins to one revolution of the tire.
The result is your rear end gear ratio.
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Joined: Mar 2007
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From: FL
Look on the inside of the drivers side door where it says axle. Here is what the code means.
19 — 3.55 non-limited slip — F-150
25 — 4.10 non-limited slip — F-150
26 — 3.73 non-limited slip — F-150/Mark LT
27 — 3.31 non-limited slip — F-150
B5 — 4.10 limited slip — F-150
B6 — 3.73 limited slip — F-150/Mark LT
H9 — 3.55 limited slip — F-150
19 — 3.55 non-limited slip — F-150
25 — 4.10 non-limited slip — F-150
26 — 3.73 non-limited slip — F-150/Mark LT
27 — 3.31 non-limited slip — F-150
B5 — 4.10 limited slip — F-150
B6 — 3.73 limited slip — F-150/Mark LT
H9 — 3.55 limited slip — F-150
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rpxr400, the problem with this method when using an open differential is that the axle (i.e. both tires) must turn one full revolution to accurately asses the gear ratio. With an open diff it is very easy for some of the turning motion to get used up by the spider gears and thus skew the ratio you come up with.
If you leave one tire on the ground you won't get the true ratio by turning the other one turn because the open differential has an affect on the ratio. Likely you would have to turn it 2 turns(or maybe that's 1/2 a turn?)... I think that would probably work, but I don't have the math or the experience to say for certain. Someone else here can probably explain it better than I have.
If you leave one tire on the ground you won't get the true ratio by turning the other one turn because the open differential has an affect on the ratio. Likely you would have to turn it 2 turns(or maybe that's 1/2 a turn?)... I think that would probably work, but I don't have the math or the experience to say for certain. Someone else here can probably explain it better than I have.
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Yes - I do remember having to take up the backlash - as I'll call it, in the spider gears. I just didn't start my count until I saw the driveshaft move, as well.
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