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Old 12-21-2004, 02:31 PM   #1
robert wright
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rear gears?

I picked up a nice 87 stepside silverado 2wd last fall. It's got the 305 tbi with 700r4. It's not a powerhouse, but then again it gets great gas mileage. Right now it's covered up under 2 feet of snow.

Anyone know of an easy way of determining what the rear axle ratio is without opening up the rear? I've heard of rotating the driveline 1 turn and counting the revs of the rear wheels. Any other suggestions?
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Old 12-21-2004, 03:13 PM   #2
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If you have a tach u can use rpm, speed, and tire height to determine the axle ratio.
Here is a link with several calculators that can help u. www.csgnetwork.com/automotiveconverters.html
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Old 12-21-2004, 04:58 PM   #3
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i'd almost bet its a 2.73
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Old 12-21-2004, 05:02 PM   #4
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My '86 lists the rear end ratio in the glovebox. Yours might as well. Mine is a 3.08.

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Old 12-21-2004, 07:07 PM   #5
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yeah check the dealer option sticker in the glove box or the one in the doorjam.
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Old 12-22-2004, 02:29 PM   #6
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I took my serial number to the local GM dealer and my buddy printed me out a build sheet.
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Old 12-22-2004, 02:45 PM   #7
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Mine's a 3.08. Betting yours is too.
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Old 12-22-2004, 07:50 PM   #8
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mine was a 2.73
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Old 12-28-2004, 02:22 PM   #9
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any luck?
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Old 12-28-2004, 05:56 PM   #10
robert wright
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No luck yet, can't check the glove box idea until the damn snow stops blowing. I'm guessing it's 3.08, although 2.73 has been suggested. The last article I read said 3.08 was the tallest available though. Were 2.73 available?
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Old 12-28-2004, 06:09 PM   #11
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Even a 2.56 ratio was available. What insane string of thoughts transpired that idea we'll never know. Those gear sets serve no imaginable purpose and after being retired from their truck duty are most effective as paper weights.
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Old 12-28-2004, 07:43 PM   #12
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hey hey hey!! I'm glad i got nice and long 2.56, being as with a non-od tranny, it helps gas mileage.
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1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD
1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD
2009 Kawasaki KLX-250S too many mods for this signature
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Old 12-28-2004, 07:48 PM   #13
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look on the axle- i heard on some axles there'll be a label riveted to the axle somewhere- either the diff cover or axleshafts, and it'll have the ratio on it.
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Old 12-29-2004, 12:22 AM   #14
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usually the axle tag is gone,but if it survived,it will be on one of the upper cover bolts,you can't miss it if it's there.Honestly,if you want to know for sure,spend a few bucks on a gasket and a couple quarts of gear lube.The ratio is stamped on the ring gear,usually the # of teeth on each gear.You could probably use some fresh gear lube anyways.
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