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Old 09-03-2006, 10:49 AM   #1
mntoy
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Rear end ratio

I recently purchased two 3/4 ton trucks, how do I tell the rear end ratio's? Someone said mark and spin the rear tire and mark the drive shaft, then count the shaft turns but the shaft only spins 2.25 times. How can I tell the ratio? is there a mechanical way and is there a code to tell me what these two different trucks have?
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Old 09-04-2006, 09:07 AM   #2
daveM
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Re: Rear end ratio

You might have a code sheet on the glove box door...

GU4 - 3.08
GU6 - 3.42
GT4 - 3.73
GT5 - 4.10
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Old 09-05-2006, 06:02 AM   #3
84Custom
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Re: Rear end ratio

Count the number of teeth on the ring gear and the pinion gear.Divide the pinion number into the ring number.If ring has 41 and the pinion has 11.
41/11=3.727272...round it and it's 3.73.
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Last edited by 84Custom; 09-05-2006 at 03:55 PM.
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Old 09-05-2006, 03:07 PM   #4
MylilBowTie
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Re: Rear end ratio

my 86 has 3.42s
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Old 09-06-2006, 10:27 PM   #5
jimfulco
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Re: Rear end ratio

If you leave one rear wheel on the ground, you can turn the other one TWO full turns and count the driveshaft turns to get your ratio. Or just double the count if you go one full turn. If both wheels are up, the wheel you can't see will likely turn some and that will throw everything off.
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