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12-26-2015, 09:09 PM | #1 |
Registered User
Join Date: Sep 2011
Location: Clackamas, Or
Posts: 139
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ring and pinion question
I picked up a 1970 GMC Sierra Grande short bed(cut down). The PO decided to redrill the front and rear end to the small 5-4 3/4 lug pattern for aftermarket disc brakes and his wheels he had. I picked up a complete rear and and complete front end (hub to hub) for $100 from a buddy of mine. I measured both 12 bolts to make sure they were the same width. After yanking both axels out of both rear end I looked at the ring and pinions. Both are 3.07 ratios, the rear end under the truck is 14:43 tooth count and the spare rear end is 13:40 tooth count. Why would GM use 2 seperate ring and pinion setups for the same ratio?
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12-26-2015, 09:31 PM | #2 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: ring and pinion question
Quote:
My thought is one may be an aftermarket replacement? The 14:43 would be correct for a 12 bolt 3:07 gear in a truck rear end.
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Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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12-26-2015, 09:38 PM | #3 |
Registered User
Join Date: Sep 2011
Location: Clackamas, Or
Posts: 139
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Re: ring and pinion question
The ring gear in the truck is stamped 3817779 14:43 GM 4-70 1. Im assuming 4-70 is april 1970. The ring gear in the spare rear end is stamped 14018118 13 40 GM 1 80 1.
The spare rear end stamping is hard to read since tooth cuts are half way into the stampings if that makes sense. I was told the spare rear end came out of a early 70's truck but im thinking its from a 1980? |
12-28-2015, 10:43 PM | #4 |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,722
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Re: ring and pinion question
Is the ratio marked? The math suggests that the 43/14 = 3.0714 would round down to 3.07 and the 40/13 = 3.0769 which would round up to 3.08.
This is a great example of how the numbers can and do vary a little (4.10 vs 4.11 or even 4.09 depending on the axle manufacturer) and exactly how that works. Don't know enough about 1/2 ton square bodies to know if 3.08 was the common three-oh gear or not. Is this a leaf spring truck I assume? Are perches narrow on both for the 2.25" springs? An '80 model 12 bolt would have perches for 2.5" springs.
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12-28-2015, 11:45 PM | #5 |
Registered User
Join Date: Sep 2011
Location: Clackamas, Or
Posts: 139
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Re: ring and pinion question
the 80 rear end is a spare i bought off a buddy. He was told it was an early 70's 12 bolt but that proved to be wrong. Im not using anything from that rear end except the actual axle shafts.
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12-29-2015, 12:19 AM | #6 |
All about them K’s
Join Date: Jun 2014
Location: Land of Entrapment
Posts: 6,416
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Re: ring and pinion question
I'm not sure if it helps or not but my 3100 is on an 88 k/5 frame and it's got the 43/14 set in it. The rear end is from a mid 70s half ton but the front is date coded to match the frame so I'm sure it's original. If all you need is the axles than it shouldn't make a difference. Honestly if one set was 3:07 and one was 3:08 it wouldn't make a big enough difference to worry about. Look at the Dana front 4:10 and Eaton rear 4:11 K/20s for example.
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