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Old 06-26-2018, 08:24 PM   #1
Sawlog
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12 bolt rear end

I'm trying to figure out what rear end I have in my 69 c10.
I guess GM made a type 2, 3, and 4 housing?
I would like to get a posi unit and different gears for my truck sometime.
How do I know what's what?
I have found 4 different sets of numbers on the housing.
HB0909 IS ON top of the passenger side axle tube.
NF3896838 is on the passenger side pumpkin facing the front.
GM58 is 9n the driver side pumpkin facing the front.
H228 is on the driver side pumpkin facing the rear.
I do know I have a 3.07 or 3.08 gear and open rear end. I had the cover off and c9unted the teeth last year.
Thanks
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Old 06-26-2018, 09:02 PM   #2
hjewell2
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Re: 12 bolt rear end

if it is a 3;08 you have a series three carrier
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Old 06-26-2018, 09:20 PM   #3
Sawlog
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Re: 12 bolt rear end

Quote:
Originally Posted by hjewell2 View Post
if it is a 3;08 you have a series three carrier
Does that mean when I go to buy a posi unit and gears that I have to make sure it's a series 3 unit?

Last edited by Sawlog; 06-26-2018 at 09:51 PM.
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Old 06-26-2018, 09:33 PM   #4
mongocanfly
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Re: 12 bolt rear end

("Does that mean when I go to buy a pork unit and gears that I have to make sure it's a series 3 unit?")

Pork unit?
Just make sure your new posi carrier and gears are compatible....
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Old 06-26-2018, 09:51 PM   #5
Sawlog
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Re: 12 bolt rear end

Thank you
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Old 06-26-2018, 11:28 PM   #6
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Re: 12 bolt rear end

The 2, 3 or 4 series, refers to the carrier. It has nothing to do with the housing other than fitting a truck 12 bolt. Each series of carrier is compatible with only a certain range of gear ratios. The lowest gear ratio available for a 3 series carrier is a 3.42. If you are wanting 3.73's or lower, you will need a 4 series carrier.
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Old 06-27-2018, 06:43 AM   #7
Sawlog
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Re: 12 bolt rear end

Quote:
Originally Posted by Captainfab View Post
The 2, 3 or 4 series, refers to the carrier. It has nothing to do with the housing other than fitting a truck 12 bolt. Each series of carrier is compatible with only a certain range of gear ratios. The lowest gear ratio available for a 3 series carrier is a 3.42. If you are wanting 3.73's or lower, you will need a 4 series carrier.
So if I want to go from my series 3 carrier to a series 4 so I can have 3.73 gears, then I need to buy a new carrier? Or is a new posi unit with 3.73 gears all I need?
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Old 06-27-2018, 07:51 AM   #8
A1971Blazer
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Re: 12 bolt rear end

there is a gear set available so that you don't have to change the carrier.....this one from Yukon Gear will change your 3.08 to a 3.73 by utilizing a "thick" gear...with your existing carrier
https://www.randysworldwide.com/product/yg-gm12t-373t/
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Old 06-27-2018, 01:31 PM   #9
mongocanfly
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Re: 12 bolt rear end

But hes wanting posi so he may as well change the carrier.....depending on which one he goes with...
Just make sure it's a 4 series
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1981 c30 lq9 nv4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598
1955.1 ls3 tr6060...(under construction)(on hold)
2013 gmc z71. (daily driver)
Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563
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Old 06-27-2018, 01:52 PM   #10
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Re: 12 bolt rear end

Quote:
Originally Posted by mongocanfly View Post
But hes wanting posi so he may as well change the carrier.....depending on which one he goes with...
Just make sure it's a 4 series
Sorry....I missed that part....for sure that would require a new/different carrier....I use TrueTrac myself....
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Old 06-27-2018, 01:58 PM   #11
mongocanfly
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Re: 12 bolt rear end

Thumbs up for trutrac...
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