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02-08-2019, 12:19 AM
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#1 |
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Registered User
Join Date: Dec 2008
Location: wellington ohio
Posts: 55
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1981 STD gear ratio
HELP! I am working on a 81 C-10 two wheel drive 10 bolt with some rear end issues. Build tag said that is a GQ1, STD RATIO. Question is what is the standard ratio? I have a 10 bolt GU4, 3:08 gear in it and would like to use it if it's close to the GQ1.
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Racerface Wellington, Ohio  Freedom Isn't Free!GO BUCKEYES!!! Toys: 68 C-30 327-400turbo 68 C-30 Open Road Camper 327-400turbo 81 GMC Sierra 1500 250-350turbo Long Bed 83 K-10 4X4 Scottsdale |
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02-08-2019, 02:37 AM
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#2 |
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Registered User
Join Date: Dec 2018
Location: Alberta
Posts: 71
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Re: 1981 STD gear ratio
Did you look at the plate on the diff itself?
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02-08-2019, 07:50 AM
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#3 |
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Registered User
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,658
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Re: 1981 STD gear ratio
Unless you know the history of the truck back to first sale, don't trust the build tag. A PO could have changed the gear set.
Simplest is do the spin the tire, count the drive shaft rotations test. If the rear end is off the truck, just count teeth on the gears. |
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02-08-2019, 08:20 PM
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#4 |
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Registered User
Join Date: Dec 2008
Location: wellington ohio
Posts: 55
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Re: 1981 STD gear ratio
At the moment axle is still in the truck. The truck has been in family since 1981. Guess I'll do the old rotation trick. Just thought it was odd GM just calls it "The STD Ratio". Thanks for your time Big Moose and Dead Parrot, stay warm!
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Racerface Wellington, Ohio Freedom Isn't Free!GO BUCKEYES!!! Toys: 68 C-30 327-400turbo 68 C-30 Open Road Camper 327-400turbo 81 GMC Sierra 1500 250-350turbo Long Bed 83 K-10 4X4 Scottsdale |
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02-08-2019, 09:08 PM
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#5 |
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Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,284
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Re: 1981 STD gear ratio
Need more detail in terms of engine and trans but the "most base" ratio is 2.73 .
https://www.gmheritagecenter.com/doc...olet-Truck.pdf (Powertrain charts shown on page 12 - California only - and page 13 - all others - of the pdf) The reason the base axle is not called out specifically (designated by GQ1) is because it changes numerically based on other powertrain considerations, per the charts. The optional axles get called out by name because the numerical ratio always stays the same as the RPO code. Bottom line is, as Dead Parrot said, no telling what's in there after all this time. K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ Last edited by Keith Seymore; 02-09-2019 at 09:49 AM. |
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02-11-2019, 07:25 PM
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#6 |
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Registered User
Join Date: Dec 2008
Location: wellington ohio
Posts: 55
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Re: 1981 STD gear ratio
Thanks Keith for the reply. It's a 250 - 6cyl. 350 turbo Hydro farm truck. I'll check out the GM site, thanks again.
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Racerface Wellington, Ohio Freedom Isn't Free!GO BUCKEYES!!! Toys: 68 C-30 327-400turbo 68 C-30 Open Road Camper 327-400turbo 81 GMC Sierra 1500 250-350turbo Long Bed 83 K-10 4X4 Scottsdale |
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02-11-2019, 09:11 PM
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#7 |
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Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,284
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Re: 1981 STD gear ratio
2.73:1 Federal; 3.08 for California emissions.
K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
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02-12-2019, 06:21 PM
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#8 |
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Senior Member
 
Join Date: Dec 2014
Location: Edmonton Alberta
Posts: 1,509
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Re: 1981 STD gear ratio
Mine's an 81 6 cyl (originally) I can confirm that it would be 273
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DAVE Edmonton, Alberta 1959 Apache 1967 K20 1968 C20 1970 C10 1972 GMC 2500 1981 C10 |
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02-15-2019, 01:09 AM
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#9 |
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Registered User
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 253
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Re: 1981 STD gear ratio
So,like rotate your wheel and count how many times the shaft rotates. Done!
There's your ratio. |
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02-15-2019, 05:28 AM
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#10 |
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Post Whore
 
Join Date: May 2015
Location: Alabama
Posts: 14,686
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Re: 1981 STD gear ratio
well ....sorta akart....https://shiftsst.com/articles/how-to...ear-axle-ratio
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Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver |
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02-15-2019, 06:16 PM
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#11 | |
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Registered User
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 253
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Re: 1981 STD gear ratio
Quote:
akart |
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