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

A69C10 · 02-26-2010, 09:45 AM

I have a 12 bolt 6 lug 3.73 rearend but I can get a 10 bolt 5 lug 3.08 rear. Ratios don't matter as I want a 3.42 aftermarket anyways. But which one is better 12 bolt or 10 bolt (motor is only 400 horse strong)

cdowns · 02-26-2010, 10:30 AM

12bolt truck

NINERS1 · 02-26-2010, 10:51 AM

12 bolts are stronger but 10 bolt will handle 400 hp.

**Hart_Rod** · 02-26-2010, 11:17 AM

I've got 600 hp behind my 12, I wouldn't even consider a 10....

Mike C · 02-26-2010, 07:10 PM

OK, this has been beat to death but one more time. And NOT 8.2 10 bolt, they are exceptionally weak. (passenger car from early 60's through 72)

8.5" 10 bolt has 10 bolts holding the ring gear to the case. The 12 bolt has (surprise!) 12. But the 10 bolt has larger diameter reverse thread bolts that do not require the lockwashers the 12 does. So this is a push.

8 4/8 ring gear of the 10 compared to the 12 bolts 8 7/8: mostly irrelevent 3/8 inch increase in diameter. Gear material is way more important.

12 bolt has 30 spline axles while 10 bolt has 28. This is a win for the 12. Until '88 when GM switched to 30 spline axles on the 10 bolt.

Pinion diameter is larger on the 8.5" 10 bolt, it is the same as the passenger car 12 bolt. Advantage 10 bolt on this one.

In the end, both are about the same strength wise stock. The biggest cause of failure in either is the one-wheel-peel or wheelhop. Parts are about the same price for each and aftermarket parts can be had to beef up both.

Longhorn Man · 02-27-2010, 03:28 PM

there is no reason to spend the time and money to convert a 10 bolt rear, spend that money on 5 lug axles if thats what you are after.

Keith Seymore · 02-27-2010, 03:38 PM

Guys - I have had a 8.5" ring gear 10 bolt in my Chevelle for 32 years - no problems.

The car is currently around 900 hp.

Shouldn't be any issue for a (I assume) street driven pickup truck.

K

Jacfourteen · 02-27-2010, 04:08 PM

Quote:

Originally Posted by Keith Seymore

Guys - I have had a 8.5" ring gear 10 bolt in my Chevelle for 32 years - no problems.

The car is currently around 900 hp.

Shouldn't be any issue for a (I assume) street driven pickup truck.

K

where are some pictures! You can't tease us with a 900 hp chevelle without a single pic!

AusTruck · 02-27-2010, 04:29 PM

I'm thinkin' the 8.5 rear end was also used in the Turbo Regals and guys are putting some incredible amounts of hp and torque through them without problems.

I don't know about your area, but AFAIK in Central Texas, truck 12 bolts with limited slip (or Positraction) if you like, are not common at all, and prices usually start at $500.

Oh, new limited slip rears usually run $200-300 and another $200-300 to install.

All the 73-77 GM A-bodies used the 8.5s as well as 73-up trucks. Also many of the 77-up Impalas, the late model ones coming with disk brakes too. These seem to be much more available in junkyards at better prices. Even though you might have to play with wheel backspacing, and weld mounts, its beginning to seem like the better route.

Note I do not have any of these to sell, and this does not in any way constitute an offer to sell any of these.

d10s69c10 · 02-27-2010, 04:52 PM

the 12 bolt for sure.
14 if you want something bullet proof but eats ponies

Or after you get tired of pulling out axles from the truck cause your an idiot like me.
get a **** 9"

02-26-2010, 09:45 AM	#1
A69C10 Registered User Join Date: Dec 2009 Location: McDonough,GA Posts: 123	10 bolt or 12 bolt rearend I have a 12 bolt 6 lug 3.73 rearend but I can get a 10 bolt 5 lug 3.08 rear. Ratios don't matter as I want a 3.42 aftermarket anyways. But which one is better 12 bolt or 10 bolt (motor is only 400 horse strong)

02-26-2010, 10:30 AM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 10 bolt or 12 bolt rearend 12bolt truck __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY Last edited by cdowns; 02-26-2010 at 10:31 AM.

02-26-2010, 10:51 AM	#3
NINERS1 Registered User Join Date: Feb 2006 Location: weatherford ok. Posts: 255	Re: 10 bolt or 12 bolt rearend 12 bolts are stronger but 10 bolt will handle 400 hp. __________________ 71 chevy cheyenne lwb http://s321.photobucket.com/albums/n..._tab_my_albums Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote!

02-26-2010, 11:17 AM	#4
Hart_Rod ************* Join Date: Apr 2005 Location: Pensacola, FL Posts: 17,858	Re: 10 bolt or 12 bolt rearend I've got 600 hp behind my 12, I wouldn't even consider a 10.... __________________ Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3

02-26-2010, 07:10 PM	#5
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	Re: 10 bolt or 12 bolt rearend OK, this has been beat to death but one more time. And NOT 8.2 10 bolt, they are exceptionally weak. (passenger car from early 60's through 72) 8.5" 10 bolt has 10 bolts holding the ring gear to the case. The 12 bolt has (surprise!) 12. But the 10 bolt has larger diameter reverse thread bolts that do not require the lockwashers the 12 does. So this is a push. 8 4/8 ring gear of the 10 compared to the 12 bolts 8 7/8: mostly irrelevent 3/8 inch increase in diameter. Gear material is way more important. 12 bolt has 30 spline axles while 10 bolt has 28. This is a win for the 12. Until '88 when GM switched to 30 spline axles on the 10 bolt. Pinion diameter is larger on the 8.5" 10 bolt, it is the same as the passenger car 12 bolt. Advantage 10 bolt on this one. In the end, both are about the same strength wise stock. The biggest cause of failure in either is the one-wheel-peel or wheelhop. Parts are about the same price for each and aftermarket parts can be had to beef up both. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

02-27-2010, 03:28 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: 10 bolt or 12 bolt rearend there is no reason to spend the time and money to convert a 10 bolt rear, spend that money on 5 lug axles if thats what you are after.

02-27-2010, 03:38 PM	#7
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,226	Re: 10 bolt or 12 bolt rearend Guys - I have had a 8.5" ring gear 10 bolt in my Chevelle for 32 years - no problems. The car is currently around 900 hp. Shouldn't be any issue for a (I assume) street driven pickup truck. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

02-27-2010, 04:29 PM	#9
AusTruck Registered User Join Date: Dec 2009 Location: Austin, Texas Posts: 90	Re: 10 bolt or 12 bolt rearend I'm thinkin' the 8.5 rear end was also used in the Turbo Regals and guys are putting some incredible amounts of hp and torque through them without problems. I don't know about your area, but AFAIK in Central Texas, truck 12 bolts with limited slip (or Positraction) if you like, are not common at all, and prices usually start at $500. Oh, new limited slip rears usually run $200-300 and another $200-300 to install. All the 73-77 GM A-bodies used the 8.5s as well as 73-up trucks. Also many of the 77-up Impalas, the late model ones coming with disk brakes too. These seem to be much more available in junkyards at better prices. Even though you might have to play with wheel backspacing, and weld mounts, its beginning to seem like the better route. Note I do not have any of these to sell, and this does not in any way constitute an offer to sell any of these.

02-27-2010, 04:52 PM	#10
d10s69c10 Built 4 Speed Join Date: May 2008 Location: Geneva FL Posts: 619	Re: 10 bolt or 12 bolt rearend the 12 bolt for sure. 14 if you want something bullet proof but eats ponies Or after you get tired of pulling out axles from the truck cause your an idiot like me. get a ** 9" __________________ 1969 C/10 Short Box**: 496/T-56 in worx. "To Be Old And Wise, First You Must Be Young And Stupid"

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