12-06-2012, 11:19 PM | #1 |
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Join Date: Apr 2012
Location: Las Cruces, NM
Posts: 9
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help please
I'm trying to figure out the gears on my 78 gmc c15 with 12 bolt. The casting number on the axle is 3896839N. I have tried searching this forum and the internet with no luck. Any help is greatly appreciated.
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12-06-2012, 11:27 PM | #2 |
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Location: San Antonio, Tx
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Re: help please
the only way to really do it would be to take the top off and count the teeth
have you check you spid sheet?
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San Antonio, TEXAS -Frog -I'm a valet and well I've driven BMWs, Mercedes, Porsche,Bentlys, fiats, Hondas, etc and well even do I like a few features, I love my shortbed, it dosent bore me out, just press on the gas and you'll remember why you love it. |
12-06-2012, 11:50 PM | #3 |
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Re: help please
Jack one wheel off the ground. Put a chalk mark on it at 6 oclock. Right at the bottom. Spin the tire around one revolution. Count the number of times the yoke on the driveshaft spins around. Multiply that number by 2 which will equal your gear ratio.
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12-07-2012, 05:56 PM | #4 |
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Re: help please
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12-07-2012, 05:58 PM | #5 |
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Re: help please
Not sure what the spid sheet is but I will just pop the top off and do it that way. Thanks for the help gents.
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12-07-2012, 07:26 PM | #6 |
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Re: help please
before you remove cover, loosen the fill plug on top to make sure it isnt frozen so you can refill with lube after your done
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2008 Silverado Z71 RCSB 1991 GMC Jimmy 4x4 1976 GMC Sierra C15 SWB |
12-07-2012, 11:48 PM | #7 |
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Re: help please
my 79 has a 1G80 12 bolt locker
it's got a 3.4 gear where was your number? front of the green circle?
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John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350 |
12-08-2012, 01:42 PM | #8 |
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Join Date: Apr 2012
Location: Las Cruces, NM
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Re: help please
No the numbers I found were on the front facing passenger side of the axle. But then again I did have to do some serious scraping with a spatula and scrubbing with a stiff brush to get all that gunk off the axle. It didn't help i was also doing it at night so visibility was not the best. Will take another look at it today.
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