No, not her rear end the 12 bolt rear end...

[KFreddy]

In a few weeks I will be putting a ZZ454 in my 72 SWB. This kinda forces me to update my one wheel peel, open 12 bolt rear, to something with some heft. In a perfect world where money is no objective I would be going with a Currie Enterprises, limited slip 9-nodular case with all the trimmings including rear disk brakes. $3300.00 complete. Not gonna happen My other option is to rebuild the 12 bolt that I currently have. It will most likely be an Eaton carrier and a new bearing kit. However I'm a bit confused about exactly what it is I need to make this complete. I don't know if I need a series 3 or 4. Or what other bits I will need to do the upgrade. Any thoughts or suggestions.

Thanks,

-Fred

[QKENUF4U]

i would def. go with a 4 series but thats all gonna depend on what gear ratio ya want. 3:73 down uses the 3 series and 4:11 up will use the 4-series (atleast thats how it worked when i built my 68 camaro 12 bolt rear)
your gonna need...........
correct carrier
new gears
all new bearings/seals
most of this stuff will come in a kit
and most importantly.......

someone who knows how to set it up CORRECTLY

[69gmctowrig]

OR.....if your current gear ratio is ok, Lincoln-lock it.
only cost the price of new gear oil and a hand full of welding rods. oh, and beer for me if you want me to do it

[rauto13]

Originally Posted by 69gmctowrig

OR.....if your current gear ratio is ok, Lincoln-lock it.
only cost the price of new gear oil and a hand full of welding rods. oh, and beer for me if you want me to do it

I am sure this is a joke, cause if ya weld the rearend and drive on the street, ya will eventually break it. Even with a posi, one wheel will slip as you go around curves, so as not to break something.

If I remember correctly the 12 bolt carrier in these trucks use a 3.73 and higher numerically gear ratio on a four series carrier.

I am sure someone else knows for sure.

[crazy longhorn]

12 bolt truck rears break like this....3.42 & down are 3 series on the carrier, 3.73 & numerically higher run a 4 series carrier. The cars did break differently as mentioned. IMO, for all out street perf, a 3.73 gear is just about right(assuming a 28-29" tall tire). I ran 4.10's, & while the truck really danced off the line, she reved 4000 rpms @ 78 mph. I am back on a mid 3's gear, & still have a little "grunt" + run 75 mph @ 3000 rpms on the open road. It just depends on your useage(or what you can live with), but IMO the 9" ferd is way overrated, very expensive, & for a fact takes more power to run.... L

[69gmctowrig]

No, it works. Maybe not the best route to go, but it worked in my 81 camaro, and works awesome in the Jeep too. nothing broken yet. assuming a 12 bolt is stronger than a Dana 35 (and it's just about got to be unless it's got go-kart parts in it) it should hold up fine unless you're pushing 500 horsepower or something. all you'll break is traction

[HotRod71]

If you are worried about breaking something just go with a 14 bolt FF. No worries then. We use these alot in Rock crawler applications.

[KFreddy]

Thanks for the input, I think I'm looking at a eaton 3 series carrier model 19587-010 and a new set of bearings, install kit and a Richmond 3.08 peg. I gotta keep the budget under $999.99. So I'll do what I can with what I got

Insofar as the 3 to 4 series info, this is what I found on Hot Rod Magazine online, "The Three Series carrier accepted ring and pinions that ranged from 3.08:1 to 3.73:1, while the Four Series carrier accepted ring and pinions ranging from 3.90:1 to 6.14:1"

Thanks again,

-Fred