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01-14-2012, 06:56 PM
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#1 |
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Registered User
Join Date: Nov 2011
Location: Hutto Texas
Posts: 114
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12 bolt differential ratio?
Finnally got to change my differential oil this weekend, had 14 X 43 stamped on the ring gear, after counting both gears I was satisified it was a 307: 1 differential. Question is I thought these came in 308 ratios ? Whats up?
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01-14-2012, 08:57 PM
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#2 |
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Registered User
Join Date: Mar 2011
Location: Bandera, Texas
Posts: 251
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Re: 12 bolt differential ratio?
I think a 3.08 in a 12 bolt is a 40-13 tooth count. Are you sure it's a GM 12 bolt? Sounds like a Dana 30 and would be a 3.07.
Last edited by Max1775; 01-14-2012 at 09:03 PM. |
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01-15-2012, 12:48 AM
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#3 |
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60-66 Nut
  Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,246
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Re: 12 bolt differential ratio?
I believe the truck 12 bolts had a 3.07 ratio, and the passenger car 12 bolts had a 3.08 ratio. Those two numbers get swapped around during conversations frequently.
__________________
Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE |
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01-15-2012, 01:31 AM
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#4 |
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Registered User
Join Date: Jun 2011
Location: Vancouver, WA
Posts: 92
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Re: 12 bolt differential ratio?
I gave up on changing my 4:56 axle in my '65 C20 over to a 14 bolt, don't mean to hijack your thread. I decided to just change the ratio, although I have heard 4:11 is the best I can do?
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01-15-2012, 06:42 AM
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#5 |
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Registered User
Join Date: Nov 2011
Location: Hutto Texas
Posts: 114
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Re: 12 bolt differential ratio?
Yes I checked and my rear end is defently a GM 12 bolt, the 307 gears work out just right for the road.
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01-15-2012, 11:29 AM
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#6 |
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Registered User
Join Date: Nov 2009
Location: Cremona AB Canada
Posts: 370
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Re: 12 bolt differential ratio?
Truck 12 bolts came in both ratios for some weird reason, and the 14 bolt (73-2000) can be had with gears as tall as 3.23.
__________________
62 GMC 910 short fleetside 454 super t10 14 bolt w/gov lock 70s c20 front discs (built in the 80s) 65 GMC 930 dualwheel 292 4spd all origonal 39k mi(my sons truck) 63 GMC 950 camperized school bus, (Gus the bus) 350 4speed 2 speed rear 64 GMC 950 "spare" bus 283? 4speed detroit locker 53 GMC 1ton dual wheel bus 78 GMC c25 short course off road race truck(son's truck) 355 th400 14 bolt (www.wheel2wheel.ca) 88 Peterbilt 379 longhood (hauls race truck)   
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01-15-2012, 03:13 PM
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#7 |
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"Where were you in '62?"
Join Date: Jul 2004
Location: Cleveland County, North Cackalacky
Posts: 5,013
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Re: 12 bolt differential ratio?
1960-1966 Chevy/GMC Pickup Truck Specs & Engine/Trans/Axle ID's
http://67-72chevytrucks.com/vboard/s...d.php?t=327764   
__________________
PROJECT: "FULL METAL YELLOW JACKET" 1962 Chevy C-10 Stepside Shortbed Nostalgia Pro/Street Pickup Truck PROJECT: "FULL METAL YELLOW JACKET Build Thread What Are You Workin' On? - 1Bad62ChevyPickup PROJECT: "TYRANNORAMBLER REX" 1969 AMC Rambler American Nostalgia Pro/Street Youtube Channel: Father Son Projects Youtube Channel: 2TIMOTHY2FITHTEEN  "North and South Carolina Folks Click Here!" (((( ~ I have Parts For Sale & Miscellaneous Stuff ~ )))) "Well being as there's no other place around the place, I reckon this must be the place, I reckon...Nyuk Nyuk Nyuk" -Curly Howard Ph.D. |
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01-15-2012, 05:22 PM
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#8 |
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Registered User
Join Date: Feb 2009
Location: Lebanon, Oregon
Posts: 130
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Re: 12 bolt differential ratio?
Hey, PureBred, with the 3.07 gearset, what engine & tranny do you have and what is your engine RPM @ 60 mph?
I have 3.73 in my 1966 C-10. 283 and 4spd SM420 tranny @ 60 = 2800 rpm or so. This doesn't get much highway use, due to the high rpms. Back country roads and secondary highways are best.
__________________
Eugene, Oregon Lucy's Limousine 1966 C-10 LWB 283 w/ 2bbl, OE carb and dist. 4 spd (granny 1st) w/ 3.73 rear end |
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01-15-2012, 08:14 PM
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#9 |
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Registered User
Join Date: Nov 2011
Location: Hutto Texas
Posts: 114
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Re: 12 bolt differential ratio?
I have a 350 with a turbo 350 trans, at 60 about 2100.
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01-16-2012, 12:18 AM
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#10 | |
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60-66 Nut
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,246
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Re: 12 bolt differential ratio?
What size rear tires are you running?
Quote:
__________________
Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE |
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01-16-2012, 03:50 PM
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#11 |
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Registered User
Join Date: Mar 2011
Location: Bandera, Texas
Posts: 251
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Re: 12 bolt differential ratio?
Learn something new everyday.
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