Wanting rear disc, but strange 12-bolt - The 1947 - Present Chevrolet & GMC Truck Message Board Network

muddpile · 01-28-2013, 10:22 AM

Greetings! Having rolled on 20x10 Coys C5's for three years or so now, and having no back brakes for two of them, I've decided that I should take the plunge and upgrade to a standard 11" rear disc kit, as it's safer and looks awesome. My question is, should any one of them fit? I like dealing with CPP, but I have a really weird 12 bolt for a truck apparently, as it has a round cover. I was told it was swapped in from an 80's burb or something, but I don't think so... Here's a pic. The bolt pattern is 5 on 5, so standard truck stuff.

geezer#99 · 01-28-2013, 10:54 AM

Looks like chevy Impala 12 bolt mid 70's. Some of them had 5x5.

SS Tim · 01-28-2013, 11:09 AM

Agree that looks like a full size chevy car like and Impala or wagon rear end.

**Ol Blue K20** · 01-28-2013, 11:50 AM

Judging from that cover I'm thinking full size olds,pont or buick. Need to check casting numbers against GM parts book.

muddpile · 01-28-2013, 08:32 PM

Here's a 70's Caprice/Impala kit
http://www.summitracing.com/parts/sum-bk1325-x

Here's a 70's C10 kit
http://www.summitracing.com/parts/sum-bk1401-x

Here's a BOP kit that goes from the 50's to the 90's
http://www.summitracing.com/parts/sum-bk1322-x

The BOP kit has the small bolt pattern and small rotors, so it's out, but the other two look pretty good. Unfortunately, they're different... So looks like I'm back to the drawing board as they don't look to be interchangeable.

Casting numbers have been mentioned, where are those located? The diff has been painted since the pic, and the truck has a 5/7 drop, so they won't be stupid easy to find, but I'm willing to dig if someone knows where they are. Thanks.

67gmcclassic · 01-28-2013, 08:46 PM

i have a 70 chevelle with a 12 bolt, it looks a lot like that.

muddpile · 01-29-2013, 07:44 PM

www.summitracing.com/parts/sum-bk1323-x

Hmmm. Another car, another part number. It appears the Chevelle is 4.75" as well, so it's not the one either. I have a Toronado front end in my other truck, and it is 5x5, so I know some larger GM cars are. I wonder which will bolt on, or what the differences can be out at the hubs, if any?

ratrod67 · 01-29-2013, 08:34 PM

The casting number is usually on the centersection between one of the ribs on the yoke side. The top passenger side axle tube will have the codes to tell what is in it.

mrolds88 · 01-29-2013, 09:10 PM

Chevy car 12 bolt has a upside down V in the cover. 99% sure its an Olds 12 cbolt. They used them through at least 70, but I think they may have gone to 72 maybe. You can get gears/posi for them but cost prohibitive. I'd go for a regular truck 10 or 12bolt

01-28-2013, 10:22 AM	#1
muddpile Registered User Join Date: Dec 2004 Location: Saskatchewan, Canada Posts: 1,371	Wanting rear disc, but strange 12-bolt Greetings! Having rolled on 20x10 Coys C5's for three years or so now, and having no back brakes for two of them, I've decided that I should take the plunge and upgrade to a standard 11" rear disc kit, as it's safer and looks awesome. My question is, should any one of them fit? I like dealing with CPP, but I have a really weird 12 bolt for a truck apparently, as it has a round cover. I was told it was swapped in from an 80's burb or something, but I don't think so... Here's a pic. The bolt pattern is 5 on 5, so standard truck stuff. __________________ 1964 Chevy Short Fleet: Tornado 1972 Chevy C10: Fast Orange Secondaries Wide Open Last edited by muddpile; 01-28-2013 at 10:32 AM.

01-28-2013, 10:54 AM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Wanting rear disc, but strange 12-bolt Looks like chevy Impala 12 bolt mid 70's. Some of them had 5x5.

01-28-2013, 11:09 AM	#3
SS Tim Registered User Join Date: Aug 2010 Location: Edwards, CA Posts: 7,507	Re: Wanting rear disc, but strange 12-bolt Agree that looks like a full size chevy car like and Impala or wagon rear end. __________________ Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID Blazer SPID Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders Do you have a 1972 Plaid Pickup? Plaid Blazer ** Plaid Suburban

01-28-2013, 11:50 AM	#4
Ol Blue K20 Proprietor of Dale's Corner Join Date: Nov 2012 Location: Vacaville , CA Posts: 16,247	Re: Wanting rear disc, but strange 12-bolt Judging from that cover I'm thinking full size olds,pont or buick. Need to check casting numbers against GM parts book. __________________ "Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man R.I.P. FleetsidePaul

01-28-2013, 08:32 PM	#5
muddpile Registered User Join Date: Dec 2004 Location: Saskatchewan, Canada Posts: 1,371	Re: Wanting rear disc, but strange 12-bolt Here's a 70's Caprice/Impala kit http://www.summitracing.com/parts/sum-bk1325-x Here's a 70's C10 kit http://www.summitracing.com/parts/sum-bk1401-x Here's a BOP kit that goes from the 50's to the 90's http://www.summitracing.com/parts/sum-bk1322-x The BOP kit has the small bolt pattern and small rotors, so it's out, but the other two look pretty good. Unfortunately, they're different... So looks like I'm back to the drawing board as they don't look to be interchangeable. Casting numbers have been mentioned, where are those located? The diff has been painted since the pic, and the truck has a 5/7 drop, so they won't be stupid easy to find, but I'm willing to dig if someone knows where they are. Thanks. __________________ 1964 Chevy Short Fleet: Tornado 1972 Chevy C10: Fast Orange Secondaries Wide Open

01-28-2013, 08:46 PM	#6
67gmcclassic Registered User Join Date: Jan 2013 Location: Louisburg, NC Posts: 25	Re: Wanting rear disc, but strange 12-bolt i have a 70 chevelle with a 12 bolt, it looks a lot like that.

01-29-2013, 07:44 PM	#7
muddpile Registered User Join Date: Dec 2004 Location: Saskatchewan, Canada Posts: 1,371	Re: Wanting rear disc, but strange 12-bolt www.summitracing.com/parts/sum-bk1323-x Hmmm. Another car, another part number. It appears the Chevelle is 4.75" as well, so it's not the one either. I have a Toronado front end in my other truck, and it is 5x5, so I know some larger GM cars are. I wonder which will bolt on, or what the differences can be out at the hubs, if any? __________________ 1964 Chevy Short Fleet: Tornado 1972 Chevy C10: Fast Orange Secondaries Wide Open

01-29-2013, 08:34 PM	#8
ratrod67 Registered User Join Date: Sep 2002 Location: DFW Texas Posts: 2,269	Re: Wanting rear disc, but strange 12-bolt The casting number is usually on the centersection between one of the ribs on the yoke side. The top passenger side axle tube will have the codes to tell what is in it.

01-29-2013, 09:10 PM	#9
mrolds88 Registered User Join Date: Jul 2011 Location: WV Posts: 946	Re: Wanting rear disc, but strange 12-bolt Chevy car 12 bolt has a upside down V in the cover. 99% sure its an Olds 12 cbolt. They used them through at least 70, but I think they may have gone to 72 maybe. You can get gears/posi for them but cost prohibitive. I'd go for a regular truck 10 or 12bolt



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