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I bought a Diff need to make sure its 3.9 before I install

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Old 01-19-07, 05:39 AM
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I bought a Diff need to make sure its 3.9 before I install
Hey guys I bought a diff I want to make sure its a 3.9 before I install it how can I make sure? I counted the teeth and my 4.10 had 41 of them. Now I counted the teeth on the 3.9 I just bought and it had 43 of them is this correct? Or did I buy a 4.33
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Old 01-19-07, 05:59 AM
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Give the input shaft a 360 degree turn, how many degrees did the output shaft turn?
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Old 01-19-07, 08:09 AM
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Yeah, mark a tooth on the ring gear, and one on the pinion. Spin the ring gear 1 full turn and count how many times the pinion turns around. 1 full turn of the pinion to 3.9 or almost 4 turns of the pinion, and you've got a 3.9:1
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Old 01-19-07, 08:15 AM
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Ring gear teeth divided by pinion gear teeth give you your ratio...
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Old 01-19-07, 08:40 AM
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Divide the number of teeth on the ring gear by the number on the pinion
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Old 01-19-07, 09:23 AM
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If it has more teeth then my guess is you have the 3.9. Why go with the 3.9 anyways?
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Old 01-19-07, 10:50 AM
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4.10 = 41/10 (ring gear/pinion gear)

3.90 = 43/11
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Old 01-19-07, 05:05 PM
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Originally Posted by BackyardSog
If it has more teeth then my guess is you have the 3.9. Why go with the 3.9 anyways?
cough cough ls1

-dj
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Old 01-20-07, 02:46 AM
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Thanks Jim that makes it easy.


Originally Posted by jimlab
4.10 = 41/10 (ring gear/pinion gear)

3.90 = 43/11
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