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06-24-2020, 02:25 AM
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#1 |
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Registered User
Join Date: Jan 2014
Location: Fort Collins CO
Posts: 124
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Gear Ratio
I recently purchased a SRW 1986 K30 4x4 pickup with SBC & 4 speed.
Looks to have a Dana 60 in front and 14 Bolt rear differential. Will be pulling cover to verify but should be 3:73, 4:11 or 4:56 gears correct? Hoping to clean tube for ID info and see if ID tag is still on cover... Will probably be installing this in my 1968 Suburban 4x4 Cummins build... |
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06-24-2020, 02:50 AM
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#2 |
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Post Whore
  
Join Date: May 2015
Location: Alabama
Posts: 14,598
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Re: Gear Ratio
More than likely it would be one of those...the mil trucks usually came with 4.56s...I have axles with 3.73s and 4.10s...be easy enough to know when you pull the covers...should be a stamping on the ring gear..
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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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06-24-2020, 06:14 PM
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#3 |
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Registered User
Join Date: May 2012
Location: horseheads,ny rust belt
Posts: 2,794
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Re: Gear Ratio
the front 60 might still have the ratio tag on a cover bolt . if not clean up the tube on the long side and look for the stamped in BOM # .
i prefer to pop covers to know 100% what you have and its a good time to change the oil most of the time its NASTY and way over due .
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77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. |
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06-26-2020, 03:15 PM
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#4 |
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Registered User
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 253
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Re: Gear Ratio
Rotate the rear tire and count the turns on the drive shaft. My 1984 K 20 is 4:11 or 4:10.
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06-27-2020, 10:35 PM
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#5 | |
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Registered User
Join Date: Jul 2014
Location: North-central Virginia
Posts: 1,099
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Re: Gear Ratio
Quote:
Alternately, Rotate one tire through two revolutions, and count the driveshaft revolutions. This is your ratio. The reason the second method works, is because of the differential.
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1987 C6P V20 truck, 2010 LMG 5.3, AFM delete, 2010 Camaro exhaust manifolds, 1997 nv4500, 1991 np241c, hydroboost, 2005 14bff axle & driveshaft, drop-n-lock gooseneck, 4.10 gears, stock suspension, rims, and tires. Still a work in progress. Any questions or suggestions are welcome! |
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06-27-2020, 11:38 PM
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#6 | |
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Senior Member
Join Date: Jun 2019
Location: Midway USA Kentucky
Posts: 540
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Re: Gear Ratio
Quote:
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http://67-72chevytrucks.com/vboard/s...d.php?t=791250 |
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06-28-2020, 06:33 PM
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#7 |
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Senior Member
Join Date: Oct 2009
Location: Godley, TX
Posts: 17,937
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Re: Gear Ratio
Is there a gear ratio called out on your SPID? If not, it was very likely a 4.56 originally.
Also, if you have a tach and can tell us your rpm at a given speed and tire diameter, can tell you what ratio you have. |
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