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#1 |
Registered User
Join Date: Aug 2009
Location: Wiltshire, UK
Posts: 157
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'63 12 bolt rear
Will it physically take a 2:73 diff and if so are there any outlets that can supply this? Stock gearing is killing me, even on 28.5" tyres!
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'63 C10 Longbox fleetside '94 C1500 Sierra ex-USAF beater |
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#2 |
Registered User
Join Date: Jan 2013
Location: Calgary Alberta
Posts: 1,166
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Re: '63 12 bolt rear
My understanding is no, unless the carrier is also changed. Something about series 3 or 4.
I had a 64 3.73 in my 66 for a while. Took it out and put in a 3.07 from a 71, which still has the six studs but is 1 1/2 wider. You might get better results with putting in an overdrive transmission. |
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#3 |
Registered User
Join Date: Aug 2015
Location: Asheville NC
Posts: 494
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Re: '63 12 bolt rear
I don't have an answer but google Randy's Ring gear, I always use them for rear end parts, great products at good prices! And they are VERY knowledgeable
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#4 | |
Registered User
Join Date: Aug 2009
Location: Wiltshire, UK
Posts: 157
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Re: '63 12 bolt rear
Quote:
How have you found the 3.07? What trans are you running? I took the cover off The axle on my '79 donor this evening and it has a 3.07 in it. I am aware of the whole series thing with the 12 bolts but don't understand it.
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'63 C10 Longbox fleetside '94 C1500 Sierra ex-USAF beater |
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#5 | |
Registered User
Join Date: Aug 2006
Location: Athens, Georgia
Posts: 1,456
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Re: '63 12 bolt rear
Quote:
The thickness of the ring gear is different, depending on what the gear ratio is. It's in the manufacturing process. The "case break" (series) are specific to those different ring gear thicknesses. If you put the wrong ring gear on a case, it'll either be too far or too close to the pinion gear. I don't know what the actual "case breaks" are on the 12-bolt... On the Dana 44, it's 3.90-up, and 3.73 down (and there might be a third case break farther down). Oddly, Mopar 8 3/4 and Ford 9-inch drop-out rear ends don't have case-breaks--they just make the ring gear itself thicker or thinner so they all ride on the same differential case. -Brad
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'61 Suburban daily driver: off the road due to 180-pound 8-pt buck! '62 K-10 long-step project '61 C30 Camper, aka "Valdez" There's no cool like Old School |
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#6 |
Registered User
Join Date: Jan 2013
Location: Calgary Alberta
Posts: 1,166
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Re: '63 12 bolt rear
The 3.07 is sort of OK I guess as far as rolling down the highway goes. I have the 4sp manual and hate changing gears so I see a 700R4 in the future. Might have to go back to the 3.73 though if I do that.
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#7 |
Registered User
Join Date: May 2009
Location: Unincorporated County, TX
Posts: 172
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Re: '63 12 bolt rear
The more teeth on the ring gear, the thicker it is, so the carrier has a thinner flange. 2.56-2.73 is Series 2. 3.08-3.73 is Series 3, and 3.90 up is Series 4.
If you don't need posi you can find plentiful series 2 carriers with 2.73 gears in late 70's square bodies. Sometime in the early eighties they dropped the 12 bolt, '81 maybe? If you want posi you'll be looking at Auburn or Eaton aftermarket.
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Don't let my username fool you, I have become brand blind. Cool is cool, period. ![]() 1965 C-10 - "Whipping Post" 1958 Biscayne - "Ruby" 1961 IH Scout 80 - "Gaucho" (My wife's new project) 1938 Chevy - unstarted project. |
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#8 | ||
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,248
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Re: '63 12 bolt rear
On the truck 12 bolt if you wan to switch to a gear higher than 3.73, which is what you likely have, you will have to change the carrier. Since the '63 & '64 12 bolts have 17 spline axles, you will have to either install your 17 spline spider gears into the new carrier, or switch to 30 spline axles. In my opinion the 3.42 gear is a good all around gear, but your rpm's will still be a little high for highway driving. If you go with a 3.07 gear or higher, you will likely have to use 1st gear for everyday driving. This is of course dependent on what engine you have.
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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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#9 |
Registered User
![]() Join Date: Jun 2006
Location: Maple Valley, WA
Posts: 1,913
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Re: '63 12 bolt rear
The whole reason for those gears is because of that tiny little engine that doesn't make any power and putting 2.73 gears in it is going to kill any acceleration you have now. Since you don't want to switch trans buy 33" tall tires instead.
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Custom Painter/Restoration Specialist 1965 GMC 3/4 Ton LB SOLD? 1964 Chevy El Camino in full restoration 1991 Chevy S10 288K+ miles 2nd Owner SOLD 2020 RAM 1500 Warlock |
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#10 |
Registered User
Join Date: Jan 2013
Location: Calgary Alberta
Posts: 1,166
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Re: '63 12 bolt rear
Yes, IMO 273 is too high.
With 3.07 I still don't get it into 4th very much when driving in the city. A lot of it is done in third. 3.73 would be better for on the farm or in the city at 30 - 40 MPH. On the highway though the 3.07 lets you cruise nicely at 60 - 65 MPH. And it will go still go faster if you want it to. |
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#11 |
Registered User
Join Date: Jan 2015
Location: Anaheim, ca
Posts: 120
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Re: '63 12 bolt rear
I have 3.42's with a granny 4spd, 400sbc. It's ok around town, still not enough gear for freeway speeds, imo. 3.73's were awesome around town. 3.07 in my future.
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#12 |
Registered User
Join Date: May 2009
Location: Unincorporated County, TX
Posts: 172
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Re: '63 12 bolt rear
Yep, got those mixed up in my mind.
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Don't let my username fool you, I have become brand blind. Cool is cool, period. ![]() 1965 C-10 - "Whipping Post" 1958 Biscayne - "Ruby" 1961 IH Scout 80 - "Gaucho" (My wife's new project) 1938 Chevy - unstarted project. |
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#13 |
Registered User
Join Date: Mar 2015
Location: Chicago Da burbs
Posts: 68
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Re: '63 12 bolt rear
BACKING PLATE WELDED TO AXLE TUBE. While on the subject of 63 12 bolts- I have a 63 1/2 ton panel, built in December 62, the backing plates are attached/WELDED to the AXLE tubes from the factory. Anybody know of a disc brake set-up that adapts to this? After hearing about the 17 spline versus 31 spline, and having a better choice of custom wheels, I may go with 5 lug aftermarket axles. I've even thought of cutting the attached DRUM backing plate down and making adapters to fit a disc brake setup, I would definitely need/keep the emergency brake and original handle as is in the cab. I've never heard of any aftermarket kit or cure for this, or have been able to find mention of it in this in forum. I've also thought I may have to replace the whole axle assembly with new/used unit because the current one is an open, no posi one. I have'nt figured cost into this yet, either. Any thoughts, ideas, comments is greatly appreciated. Dog..........over and out
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#14 | |
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,248
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Re: '63 12 bolt rear
The only way to convert a '63 12 bolt to disc brakes is to cut the original backing plate off and weld a caliper mount onto the axle tube.
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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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#15 | |
Registered User
Join Date: Mar 2015
Location: Chicago Da burbs
Posts: 68
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Re: '63 12 bolt rear
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Dog. |
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#16 |
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,248
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Re: '63 12 bolt rear
It's been many years since I have dealt with a C-clip eliminator, but if my memory is correct, I don't think they will work with any of my rear disc brackets. As for installing either on a '63 12 bolt, a flange would have to be welded onto the axle tubes that is perfectly parallel to the axle flange. That is not something easily accomplished by the average guy/gal. Of course in doing just that, the added thickness of the rear disc base plate, could be compensated for.
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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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