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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Rear Drivelines, Drive Axles and Gearing => Topic started by: daman02 on July 02, 2011, 08:39:06 AM

Title: Swap 10 bolt to 12 bolt rearend
Post by: daman02 on July 02, 2011, 08:39:06 AM
Well i'm jumpin back into my '86 2wd chevy and going to do a few things to it soon.  It has the factory 10 bolt rearend right now that i put 3.42 gears in about 5 years ago but i have a 12 bolt rearend out of a '78 big 10 i think it was that i'm wanting to put in it(both r 5x5).  I'm running a 700r4 tranny with 2500 stall but since this truck is just a cruise around and occasional dragstrip truck i'm wanting to go with 4.10 gears and possibly 3.73 to really give it some bottom end.  The tires I'm running are 295/45 18 which are 28.5" tall.  My main question is are the 2 rearends the same dimensions as far as total width and does it have the same mounts as the 10 bolt and are there any other things I would have to change to drop it in?  Also give me your opinions on which gears you think I should go with. I only ask all this because I am currently out of state but am trying to get a plan together to do it when i get back for fall.  Below is what it looks like now.


http://www.cardomain.com/ride/771450/1986-chevrolet-silverado-1500-regular-cab
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Irish_Alley on July 02, 2011, 08:45:03 AM
5x5? but the rears will swap if the 12 bolt came out of a truck. what ratio is in the 12 bolt now?
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: zieg85 on July 02, 2011, 08:51:35 AM
Only physical difference is the u-joint between the 10 and 12 bolt
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: daman02 on July 02, 2011, 08:52:47 AM
5x5? but the rears will swap if the 12 bolt came out of a truck. what ratio is in the 12 bolt now?

they are both the 5x5 bolt pattern.  the 12 bolt has 3.42 gears also.  Good to know that it will drop right it though.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: daman02 on July 02, 2011, 08:54:48 AM
Only physical difference is the u-joint between the 10 and 12 bolt

Good info there.  thanks
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: three8six on July 02, 2011, 10:52:49 AM
Can I ask why this is desirable? a 12 bolt is stronger than a 10 bolt? or are you having problems with your rear end?
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: daman02 on July 02, 2011, 11:43:31 AM
Can I ask why this is desirable? a 12 bolt is stronger than a 10 bolt? or are you having problems with your rear end?

yea the 12 bolts are stronger and have more splines on the axles as well.  Plus it I already have one and I'm planning on a pretty high hp engine in the next few years
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: three8six on July 03, 2011, 05:28:39 PM
I was just curious. Please post details. I have 10 bolt in my truck and I got a good 12 bolt just hanging out in the shop on an identical frame. I thought the ring gear was only like 8 7/8's?
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Irish_Alley on July 03, 2011, 11:01:32 PM
if they are stronger i dont think its that much stronger 10 bolt ring gear is 8 1/2 and the 12 bolt is 8 7/8 but the 10s where only 1/2 ton and the 12s where 3/4
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Blazin on July 04, 2011, 07:20:46 AM
I have never in all my years working on and playing with these trucks seen a 12 bolt in a 3/4 ton! Only rear offered in 3/4 ton was a 14 bolt full floater, and a 14 bolt semi floater.
12 bolts are not that much stronger than a 10 bolt. You will need a crossover u joint, The cross width is shorter on a 12 bolt, and the cap diameter is smaller on a 12 bolt.
All Chevy 1/2 ton 2 wheel drives are the same lug pattern.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: chevymanrob on July 04, 2011, 10:21:22 AM
the way i understand it is that the truck stuff is VERY similar in durability between 10 and 12 bolt stuff. the car stuff is where the difference is noticable. i know the A body 12 bolt i had was awesome. and if it were my pennies i would just work with what i have. you can build a really strong 8.5" for not alot of $.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: daman02 on July 04, 2011, 01:10:39 PM
the way i understand it is that the truck stuff is VERY similar in durability between 10 and 12 bolt stuff. the car stuff is where the difference is noticable. i know the A body 12 bolt i had was awesome. and if it were my pennies i would just work with what i have. you can build a really strong 8.5" for not alot of $.

I always read that the 12 bolts were stronger but i never thought about them refering to the 10 bolt car which is 7.5" i think.  I might just leave the 10 bolt in and work with that like you suggested.  This is why forums are so great.  I was about ready to order gears, mini spool, and bearing kit for the 12 bolt when I already have all that for the 10 bolt.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: chevymanrob on July 04, 2011, 01:33:43 PM
there are guys with the 8.5" Gbody rears (grand national and 442s) WELL into single digit 1/4 times....thats 500+ horsepower. i am only going to run the 10 bolt in my truck.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: three8six on July 04, 2011, 05:39:11 PM
10 bolts in F/S trucks are 8.5inch
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Irish_Alley on July 04, 2011, 11:07:39 PM
see blaze thats what i thought also but then i went on
http://coloradok5.com/axleguide.shtml
and i thought they have there stuff inline and knew more than me lol
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Blazin on July 05, 2011, 05:32:19 AM
Pretty sure they missed on that one. I could be wrong, it has happend once before!  :)
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Irish_Alley on July 05, 2011, 10:39:53 AM
I hear ya ;D
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: Captkaos on July 21, 2011, 05:03:47 PM
12bolts trucks are NOT stronger than 10bolts.  12bolt cars yes, truck no.
12 trucks have a smaller pinion shaft than 10bolts the only other difference is the size of the ring gear and you aren't gaining much by loosing pinion size.  So it is a wahs in my opinon.,
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: daman02 on July 22, 2011, 09:28:02 PM
Yes i have since abandoned the 12 bolt project and decided to just throw some 4.10's with a mini spool in my 10 bolt and let it rip.  Any idea how much time can be knocked off at the track going from 3.42's to 4.10's?  It ran an 11.7 in a 1000ft track i have near my house.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: 84scottsdale454 on July 24, 2011, 08:49:57 AM
I did a 10 to 12 bolt swap......it swaps out easy, fits right in, zero problems as long as it came out of a 12bolt c10 like mine did! Go for it, 2easy man!
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: VileZambonie on July 24, 2011, 11:45:04 AM
I've heard it all but from experience I've grenaded and seen grenaded more 10 bolt than 12 bolts. Typically the carrier breaks at the pinion shaft as well as the differential gears more commonly in the 10 bolts. When this happens it usually trashes the entire housing. The most common failures I've seen with 12 bolts were a result of bearing failure.

Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: 84scottsdale454 on July 24, 2011, 12:30:40 PM
I'm sure most people would agree when I say "if u take care of ur truck,then it'll take care of you" no rearend is gonna hold up if u dog your truck, don't put 2 much thought into it,just do what u know will work, 12bolt will work and hold up good, mine does and I hot rod my truck some and if the torque from my 454 won't break my 12bolt then you'll be doing just fine, later dude
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: chevymanrob on July 24, 2011, 12:39:27 PM
i swapped from 3.55s to 4.10s in my el camino and went from a 12.09 to 11.86 (1/4 mile). i think about 2 tenths should be pretty close. possibly a little more or less depending on where you cross the stripe rpm-wise and where your motor wants to be.
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: bigchevy74 on July 26, 2011, 04:30:14 PM
i have a 10 bolt with 4.10's and im pushing 400hp i want to keep my 10 bolt what can i do to it to make it stronger.....locker???
Title: Re: Swap 10 bolt to 12 bolt rearend
Post by: chevymanrob on July 26, 2011, 05:31:23 PM
well other than making sure the bearings are good to go there isnt a whole lot i can suggest. i do personally like the powertraxx lockers (had one in the past). if you have an open diff but like your gear then definately go that route...no gear setup needed! other than spinning a carrier bearing in my Abody 12 bolt i didnt have any issues (11.86@113mph in a 3000 pound car).