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Old 02-01-2003, 11:11 AM
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Post rear end ratio

can any one out there tell me if it is possible to get rear end ratio out of vin#? If so here is my vin#2GOGK24T1B1 147153, ANY HELP GREATLY APPRECIATED
aLSO GLOVE BOX STICKER HAS OPTION CODE G80 LOCKING DIFFERENTIAL IT HAS A GM10.5" 14BOLT REAREND IF THIS INFO HELPS AT ALL

[ February 01, 2003: Message edited by: kors86chevy ]</p>

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Old 02-02-2003, 03:42 AM
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check the opotion sheet again it should say the gear ratio. if you cant find it check with your gm dealer,for your 81 gm 3/4 ton
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Old 02-02-2003, 08:23 AM
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why dont you jack it up and turn the wheel and see how many times the driveshaft turns.
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Old 02-02-2003, 11:44 AM
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Well wouldn't that all depend on the wheel size and tire size.I wouldn't see that ever working out unless it was all stock and even then it would hard. I don't know much about this topic but it did sound wierd.
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Old 02-02-2003, 12:19 PM
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Monte Carlo is right. Doesn't matter how big the wheel is, just one rotation of the wheel and count how many times the driveshaft turns.
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Old 02-02-2003, 12:37 PM
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It is more involved than just spin the tire and count. That doesn't work cause there are variables. Refer to this older post on this same topic.

<a href="http://www.hotrodders.com/cgibin/ubb/16/001168" target="_blank">How do you tell rearend Ratio</a>
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Old 02-02-2003, 01:31 PM
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there are NO other variables period. the rearend is a gear. if you turn one part of the gear, the other part will rotate proportionally faster or slower dictated by the ratio. if counting revolutions is not accurate or practically possible, you can also remove the rearend cover and count the teeth on the gears, example; 11 gears on the pinion, 41 on the ring: 41/11=3.7372727 (3.73) this will also be stamped on the ring gear.. come on dmorris1200 this is not rocket science
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Old 02-02-2003, 02:00 PM
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Check out how an open differential works, it gives a 2:1 ratio when one wheel is held stationary. If you don't hold one wheel still, you will get mixed readings. Open or posi diff, those are the variables. I think dmorris was more talking about the different methods as being all the different variables.

[ February 02, 2003: Message edited by: BstMech ]</p>
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Old 02-02-2003, 02:25 PM
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I have personally done the spin once method and had it not work. I even double checked the gears when I took the rear apart. I think that is why you need to rotate 10 or more times and then use an average for a more approximate guess and also keep in mind what was posted about whether or not it's posi or open. Say what you will but I have witnesed it not be accurate with my own two eyes, and I'll believe them over anything.
I think you should stay in school deuce_454, you may learn something.
And what about a beat up old rear with excessive backlash, I guess that's not a variable in the old spin it once method.

[ February 02, 2003: Message edited by: dmorris1200 ]</p>
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Old 02-02-2003, 02:44 PM
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Hey dmorris- they make wheel that you put on your axle flange that determines the gear ratio with one turn of the drive shaft (looks like a cam degree wheel). If you see one of these, notice that the open diff scale is exactly twice the degrees on the scale to get the same reading as a posi diff.
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Old 02-02-2003, 02:50 PM
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Haven't seen one yet but I would still want to average out a bunch of revolutions instead of relying on one. I have seen some pretty sloppy rears in my day, one turn could be 3.50, 3.70, etc. The more turns you do the closer your average will be. Just my opinion. And I still say (which was my first answer in the other post I linked) the best way to know for sure is to simply pop off your rear cover and count teeth. If deuce_454 had followed the link I posted he would have seen that and wouldn't have found it neccessary to post what was already posted before about counting them. This isn't rocket science deuce.

[ February 02, 2003: Message edited by: dmorris1200 ]</p>
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