Author Topic: Swap 10 bolt to 12 bolt rearend  (Read 8311 times)

Offline daman02

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Swap 10 bolt to 12 bolt rearend
« 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
'86 C10 Silverado 350 with 700r4 and 2500 stall
Dropped 2" in front and 2" in rear but soon to b 4" in rear
18x10 wheels with 295/45 18 tires

Offline Irish_Alley

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #1 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?
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth?~Sherlock Holmes

Online zieg85

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #2 on: July 02, 2011, 08:51:35 AM »
Only physical difference is the u-joint between the 10 and 12 bolt
1984 C10 Custom Deluxe 4.1L 3 on the tree
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 Custom Deluxe 5.7L 3 on the tree 2.73

Offline daman02

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #3 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.
'86 C10 Silverado 350 with 700r4 and 2500 stall
Dropped 2" in front and 2" in rear but soon to b 4" in rear
18x10 wheels with 295/45 18 tires

Offline daman02

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #4 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
'86 C10 Silverado 350 with 700r4 and 2500 stall
Dropped 2" in front and 2" in rear but soon to b 4" in rear
18x10 wheels with 295/45 18 tires

Offline three8six

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #5 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?

Offline daman02

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #6 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
'86 C10 Silverado 350 with 700r4 and 2500 stall
Dropped 2" in front and 2" in rear but soon to b 4" in rear
18x10 wheels with 295/45 18 tires

Offline three8six

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #7 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?

Offline Irish_Alley

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #8 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
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth?~Sherlock Holmes

Offline Blazin

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #9 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.
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline chevymanrob

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #10 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 $.
ex G-body drag fan. best was 11.86 on a 93 octane SBC street car.

Offline daman02

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #11 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.
'86 C10 Silverado 350 with 700r4 and 2500 stall
Dropped 2" in front and 2" in rear but soon to b 4" in rear
18x10 wheels with 295/45 18 tires

Offline chevymanrob

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #12 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.
ex G-body drag fan. best was 11.86 on a 93 octane SBC street car.

Offline three8six

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #13 on: July 04, 2011, 05:39:11 PM »
10 bolts in F/S trucks are 8.5inch

Offline Irish_Alley

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Re: Swap 10 bolt to 12 bolt rearend
« Reply #14 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
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth?~Sherlock Holmes

 


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