12 bolt - The 1947 - Present Chevrolet & GMC Truck Message Board Network

abebummy26 · 10-18-2007, 01:09 AM

I found a 73-78 chevy big 10 truck bed made into a trailer. I looked underneath it because I figured it had a 12 bolt and I was right. I'm pretty sure I could bid on it for next to nothing and get it. Should I, or not? I would also like to know how to decode the axle to tell if it is a positrac. If it is I would be a lot more tempted to buy it. I am thinking about getting it for a drag truck when I get older. The truck bed is wasted basically the only thing I would take off of it would be the tail lights because they are the chrome strip around the edge ones.

Pyrotechnic · 10-18-2007, 01:54 AM

I'd grab it if you can get it for cheap. If anything, you've bought yourself is a good 12 bolt housing and axles to work with. I would just get a good aftermarket posi unit, your choice gear ratio if the ones in there are in bad shape or not what you want, and have it built with all new bearing, seals, and whatever else it needs.

If you get it cheap, you can probably sell the trailer for scrap metal and get some money back.

abebummy26 · 10-18-2007, 02:20 AM

Yeah that's what I was thinking pull the trailer to the scrap metal yard and pull the 12 bolt and springs load it in my truck grab the lights, wheels, and tires (for rollers) and scrap everything else. Most big 10s had positrac right since the were meant to haul stuff?

**Captkaos** · 10-18-2007, 10:58 AM

Why are you wanting to get a 12bolt so desperately? What are they worth in your neck of the woods?

abebummy26 · 10-18-2007, 11:52 AM

I'm not desperate but I if I can get one for free almost if I scrap the rest of the trailer. I figured that would be a good deal for me. I have never seen one for sale, but I haven't looked.

**Captkaos** · 10-18-2007, 12:41 PM

They aren't any stronger than a 10bolt. 10Bolts have beefier pinion shafts.

Bad Karma · 10-18-2007, 02:02 PM

Quote:

Originally Posted by Captkaos

They aren't any stronger than a 10bolt. 10Bolts have beefier pinion shafts.

I seem to remember reading somewhere that you can replace the truck gears with car gears (and car pinion bearings) in the 12-bolt to get the bigger pinion. Anyone know for sure?

Pyrotechnic · 10-18-2007, 02:08 PM

The 10 bolt gets bad rap from the 7.5 inch ones that are very easily grenaded but the 8.5 units in these trucks are quite strong.

My heavy half GMC which is the equivalent to a Big 10 didn't come with a posi. All Big 10 means is 3/4 ton springs, big brakes, and heavy duty emissions.

When it comes down to it, which do you guys think is ultimately stronger? The 10 or 12 bolt ? I know a 10 bolt is plenty strong enough to where finding a 12 bolt isn't necessary, but I'd just like to know which is ultimately stronger.

**Captkaos** · 10-19-2007, 12:11 PM

Quote:

Originally Posted by Bad Karma

I seem to remember reading somewhere that you can replace the truck gears with car gears (and car pinion bearings) in the 12-bolt to get the bigger pinion. Anyone know for sure?

Not without some machine work.

BTW there is a guy on my forum selling a 12bolt for $75...

Poopski · 10-19-2007, 05:15 PM

Is the machine work to do it very costly?

**Captkaos** · 10-20-2007, 01:50 PM

Quote:

Originally Posted by Poopski

Is the machine work to do it very costly?

No idea if that is possible, just know they aren't the same.

Nolowrider · 10-20-2007, 05:23 PM

Quote:

Originally Posted by Bad Karma

I seem to remember reading somewhere that you can replace the truck gears with car gears (and car pinion bearings) in the 12-bolt to get the bigger pinion. Anyone know for sure?

Don't think so. The car pinion shaft is thicker (1.625") the truck is something like 1.4. I ordered a car set by accident and it would not fit.

abebummy26 · 10-18-2007, 12:55 PM

Thanks for the info that nixes that idea tyvm.

xtreme80 · 10-18-2007, 03:05 PM

In my neck of the woods I see 12 bolt rear end housings go all day long for 4-500 bucks, without gears... with gears they may bring even more.

abebummy26 · 10-19-2007, 12:19 AM

ttt

MylilBowTie · 10-19-2007, 06:51 PM

If its for your truck you already have the best rear for strength. Assuming that your K30 still has its original rear. I could see getting a 12 bolt for a car setup. But with the 14 bolt sf/ff out there I don't see a need for a 12 bolt. Cheaper to buy and hold more power vs the 12 bolt.

abebummy26 · 10-20-2007, 09:51 PM

Quote:

Originally Posted by MylilBowTie

If its for your truck you already have the best rear for strength. Assuming that your K30 still has its original rear. I could see getting a 12 bolt for a car setup. But with the 14 bolt sf/ff out there I don't see a need for a 12 bolt. Cheaper to buy and hold more power vs the 12 bolt.

No It wont be for my truck. I would be thinking about using for a future project maybe a drag truck?

abebummy26 · 10-22-2007, 06:24 PM

ttt

abebummy26 · 01-08-2008, 05:33 PM

I really need information on this. I know this is an old thread, but If anybody knows anything more that would be greatly appreciated. Btw I am going to school to be a machinist, so machine work is minor, to me anyways lol.

gchemist · 01-08-2008, 06:03 PM

12 bolts look better.

abebummy26 · 01-08-2008, 06:07 PM

lol thats true. Not exactly the answer I was looking for but I guess its a start.

Hoods69BadBowTie · 01-08-2008, 06:13 PM

I say go for it. If you can get it cheap and use it.

Malo83 · 01-08-2008, 07:44 PM

Quote:

Originally Posted by Hoods69BadBowTie

I say go for it. If you can get it cheap and use it.

X2

baknblk · 01-09-2008, 11:30 AM

in my neck of the woods a 12 bolt is hard to find..use to be a big deal back in the years..12 with a 4:11 was what everbody wanted ..didnt any of u guys use to race.

Alex1 · 01-09-2008, 11:37 AM

Find me a good Dana 60 and I'll trade you my 12 bolt...LOL the truck 12 bolt is not worth putting money into - not if you are going to make any power.

10-18-2007, 01:09 AM	#1
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	12 bolt I found a 73-78 chevy big 10 truck bed made into a trailer. I looked underneath it because I figured it had a 12 bolt and I was right. I'm pretty sure I could bid on it for next to nothing and get it. Should I, or not? I would also like to know how to decode the axle to tell if it is a positrac. If it is I would be a lot more tempted to buy it. I am thinking about getting it for a drag truck when I get older. The truck bed is wasted basically the only thing I would take off of it would be the tail lights because they are the chrome strip around the edge ones. __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch.

10-18-2007, 01:54 AM	#2
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: 12 bolt I'd grab it if you can get it for cheap. If anything, you've bought yourself is a good 12 bolt housing and axles to work with. I would just get a good aftermarket posi unit, your choice gear ratio if the ones in there are in bad shape or not what you want, and have it built with all new bearing, seals, and whatever else it needs. If you get it cheap, you can probably sell the trailer for scrap metal and get some money back. Last edited by Pyrotechnic; 10-18-2007 at 01:55 AM.

10-18-2007, 02:20 AM	#3
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt Yeah that's what I was thinking pull the trailer to the scrap metal yard and pull the 12 bolt and springs load it in my truck grab the lights, wheels, and tires (for rollers) and scrap everything else. Most big 10s had positrac right since the were meant to haul stuff? __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch. Last edited by abebummy26; 10-18-2007 at 02:49 AM.

10-18-2007, 10:58 AM	#4
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: 12 bolt Why are you wanting to get a 12bolt so desperately? What are they worth in your neck of the woods? __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com Last edited by Captkaos; 10-18-2007 at 10:58 AM.

10-18-2007, 11:52 AM	#5
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt I'm not desperate but I if I can get one for free almost if I scrap the rest of the trailer. I figured that would be a good deal for me. I have never seen one for sale, but I haven't looked. __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch. Last edited by abebummy26; 10-18-2007 at 12:19 PM.

10-18-2007, 12:41 PM	#6
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: 12 bolt They aren't any stronger than a 10bolt. 10Bolts have beefier pinion shafts. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

10-18-2007, 02:08 PM	#8
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: 12 bolt The 10 bolt gets bad rap from the 7.5 inch ones that are very easily grenaded but the 8.5 units in these trucks are quite strong. My heavy half GMC which is the equivalent to a Big 10 didn't come with a posi. All Big 10 means is 3/4 ton springs, big brakes, and heavy duty emissions. When it comes down to it, which do you guys think is ultimately stronger? The 10 or 12 bolt ? I know a 10 bolt is plenty strong enough to where finding a 12 bolt isn't necessary, but I'd just like to know which is ultimately stronger. Last edited by Pyrotechnic; 10-18-2007 at 02:09 PM.

10-19-2007, 05:15 PM	#10
Poopski Registered User Join Date: Jul 2007 Location: Joplin MO Posts: 35	Re: 12 bolt Is the machine work to do it very costly? __________________ 1985 Chevrolet C10 305 2wd LOOOOONG Bed Broke as a joke and funny as a funeral

10-18-2007, 12:55 PM	#13
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt Thanks for the info that nixes that idea tyvm. __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch.

10-18-2007, 03:05 PM	#14
xtreme80 Wishin' I had more money! Join Date: Feb 2007 Location: Eugene, OR Posts: 1,242	Re: 12 bolt In my neck of the woods I see 12 bolt rear end housings go all day long for 4-500 bucks, without gears... with gears they may bring even more.

10-19-2007, 12:19 AM	#15
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt ttt __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch.

10-19-2007, 06:51 PM	#16
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: 12 bolt If its for your truck you already have the best rear for strength. Assuming that your K30 still has its original rear. I could see getting a 12 bolt for a car setup. But with the 14 bolt sf/ff out there I don't see a need for a 12 bolt. Cheaper to buy and hold more power vs the 12 bolt. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

10-22-2007, 06:24 PM	#18
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt ttt __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch.

01-08-2008, 05:33 PM	#19
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt I really need information on this. I know this is an old thread, but If anybody knows anything more that would be greatly appreciated. Btw I am going to school to be a machinist, so machine work is minor, to me anyways lol. __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch. Last edited by abebummy26; 01-08-2008 at 05:36 PM.

01-08-2008, 06:03 PM	#20
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: 12 bolt 12 bolts look better. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos



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01-08-2008, 06:07 PM	#21
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: 12 bolt lol thats true. Not exactly the answer I was looking for but I guess its a start. __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch.

01-08-2008, 06:13 PM	#22
Hoods69BadBowTie Chevys Kick A$$ Join Date: Jan 2005 Location: Zootown, MT Posts: 12,699	Re: 12 bolt I say go for it. If you can get it cheap and use it. __________________ HOODS is what I answer too -'79, '77, '88 Pickup Sold, '85 Camaro, '83 T/A, '81,'83,'90 K5 Blazer All Sold -'79 3/4 ton "Big Yellow Bananna" Lifted 4spd. 39.5 TSL Swampers, The money Pit -'86 K5 Blazer Silverado 6.2 4" lift 35"s -'95 Ext. Cab Shorty 4" Tuff Country rolling 35" M/T's -'83 Monte Carlo T-Tops. 126,500 Original Miles -LATER I would rather push a Chevy then drive a ford!!

01-09-2008, 11:30 AM	#24
baknblk Registered User Join Date: May 2007 Location: southeastern ky Posts: 88	Re: 12 bolt in my neck of the woods a 12 bolt is hard to find..use to be a big deal back in the years..12 with a 4:11 was what everbody wanted ..didnt any of u guys use to race.

01-09-2008, 11:37 AM	#25
Alex1 Registered User Join Date: Jul 2007 Location: Ottawa Ontario Canada Posts: 1,156	Re: 12 bolt Find me a good Dana 60 and I'll trade you my 12 bolt...LOL the truck 12 bolt is not worth putting money into - not if you are going to make any power.

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