12 bolt rear strength

[OKGMC4]

I did a search and got a ton of info on the 12 bolts and how weak they are compared to 10 bolt 8.5" and 12 bolt car rear ends. I get that part, I don't plan on drag racing my 69, but it will be more than stock. I want to build a 5.3 to about 450 crank hp naturally aspirated and put 345 30zr19 tires on it. Will these rear ends take that kind of power and live? I only ask because I've seen ls1 F bodies get that kind of power through their weak 7.625 ring gear 10 bolts and survive. I've also seen 12 second LT1 vettes running dana 35 rear ends. Surely the truck 12 bolt is as good or better than that?

[chisler]

I can remember taking my rear diff to www.iwerearendsonly.com out my way and the guys said to me the major weakness with the 12 bolt is the carrier...prone to cracking...what they did is they stress relieved it by dressing up the whole carrier mind you this was for my 4x4 ...so you may want to ask about this out your way ..hope this helps I am a bit too far away..sorry
Frank

[Fitz]

Originally Posted by OKGMC4

I did a search and got a ton of info on the 12 bolts and how weak they are compared to 10 bolt 8.5" and 12 bolt car rear ends. I get that part, I don't plan on drag racing my 69, but it will be more than stock. I want to build a 5.3 to about 450 crank hp naturally aspirated and put 345 30zr19 tires on it. Will these rear ends take that kind of power and live? I only ask because I've seen ls1 F bodies get that kind of power through their weak 7.625 ring gear 10 bolts and survive. I've also seen 12 second LT1 vettes running dana 35 rear ends. Surely the truck 12 bolt is as good or better than that?

I don't know where you got your data but you should check your sources. I run a 650 Hp ZZ572 through a Johnny Winter built turbo 400 into a 12 bolt truck diff with 4.10 gears. That motor puts out almost 700 ft lbs of torque which is almost double what you want to run and has never broken. The truck has made over 100 passes at Southwestern International Dragway and now has 15,000 miles on it as I use it on the street and the strip with no failures.

[68350]

I have a 550hp/570tq 496 and th400(with 2800 stall) sending power to my rebuilt truck 12 bolt and haven't had an issue.

[OKGMC4]

That's awesome to hear, guys. Further proof that just because you saw it on the internet it may not be true. Some of the 12 bolt bashing I saw was on this very board. It seems like no matter what you have, someone will hate it. You do a drum to disc swap and someone will ask why you didn't just do 13" drilled rotors. You get a 5.3 and they say an LS2 would have been better. It's all relative. I already have a 3.73 posi 12 bolt and couldn't see getting rid of it. Thanks so much.

[RexDodge]

I had a 12 bolt truck rear end that I narrowed and put in my 11 second 63 nova. Ran that for over 7 years. Sold it and it's still going strong after another 5 years. The only change I suggest is the ford style axle retainers (I think I got mine from moser). With that hp the c clips make me nervous.

[kelsfine69]

454 LS7 in mine, 4:11 posi, ET drag radials 325/50-15's, no problems

[Fitz]

Originally Posted by OKGMC4

That's awesome to hear, guys. Further proof that just because you saw it on the internet it may not be true. Some of the 12 bolt bashing I saw was on this very board. It seems like no matter what you have, someone will hate it. You do a drum to disc swap and someone will ask why you didn't just do 13" drilled rotors. You get a 5.3 and they say an LS2 would have been better. It's all relative. I already have a 3.73 posi 12 bolt and couldn't see getting rid of it. Thanks so much.

Every week this board proves that opinions are just like noses...everyone has one and they are all different.

There are some very solid contributors here though and I always pay attention to them.

Good luck with your truck!