Rebuild 12 bolt or swap to 9 inch?
 

I need some advice. I’m working on a 1964 C10 with my son for him to drive when he’s 16 (he is 12 now). It is currently a bare frame, and we have just started installing a No Limit IFS, and I have No Limit goodies for the rear as well. I’m keeping the stock trailing arms, as ours are in good shape. Part of the suspension install will obviously be the rear end. The truck came with a 12 bolt truck diff, it’s open wheel with an unknown gear ration. I did a 5x5 bolt pattern on the IFS from No Limit. I’m trying to decide if I should have the 12 bolt rebuilt or swap to a 9 inch. There is a really reputable shop in Clemmons, NC who will do the rebuild and axle swap for around $2400. New gears, Eaton limited slip, etc. I’d still have to do disc brakes, which I am estimating around $500. I could also go with a complete bolt in 9 inch including brakes from Moser or Currie for not much more. I need some advice on what to do here, or if I’m missing another option to do it with a little lower impact to the budget. What say the forum? Thanks!

Re: Rebuild 12 bolt or swap to 9 inch?
 

There is absolutely nothing wrong with a truck 12 bolt. How much power will you be putting to it? $2400 seems awfully high to me to rebuild a 12 bolt. I fabricate and sell 3 different rear disc conversions for the truck 10 and 12 bolt with the 5 x 5 wheel stud pattern. The biggest problem I see with guys going with a 9" is their choice in housing ends. They end up with Ford brakes because of it. If that's what you want, then that is fine.

Re: Rebuild 12 bolt or swap to 9 inch?
 

Captainfab, thanks for the reply. I agree that the price seems high, but I’m having trouble locating other reputable shops in the area to do the rebuild. I also don’t really have a good basis for comparison on the price. I’m good with spending some money on it, but I don’t want to be in it for a ton if I can help it. I’m all about doing work on my own, but I don’t have the tools or experience to properly set up a differential. Anyone have suggestions on 1) locating other reputable shops, or 2) have a recommendation in the Triad, NC area (or even towards Charlotte)?

Re: Rebuild 12 bolt or swap to 9 inch?
 

To answer the Captainfab’s other questions, I have a 2010 LY6 (6.0 LS based truck engine) factory rated at 364hp. I see it as a good foundation, as multiple magazines have done can swaps and gone over 500hp with this engine. I don’t think that I’ll be turning it up immediately, but I’m planning on building the truck as a good foundation with plenty of room to grow. I don’t know what the overall use will end up being. It will likely start as a daily driver, but may end up doing some autocross or other racing at a later point. My plan is to give it a solid foundation, and a stout rear end. That being said, I’m good with the 12 bolt (and would honestly rather keep it). I didn’t know that Captainfab made disc brake conversions for the 12 bolt. I’ll keep that in mind as I move forward.

Re: Rebuild 12 bolt or swap to 9 inch?
 

That 2400 is sounding like full retail prices . Do your own shopping and see the prices .

Then pop the cover and see what you have now you might be surprised its clean and useable . Maybe add a lunch box locker to replace the open spider gears and a pair of 5club axles and your brake kit . And why disc rear ? Good drum work fine with disc front combo all the time .

Re: Rebuild 12 bolt or swap to 9 inch?
 

What is a "lunch box locker"?

Re: Rebuild 12 bolt or swap to 9 inch?
 

I have had this same debate in my swap to 5 lug and found I end up in a very similar place. I think the $2400 seems reasonable to me based on my research. It isn't exhaustive, but very recent.

Just a modern and streetable limited slip (truetrac, etc.) At the best price I could find was $850+. Add in new axles, ring and pinion, seals, bearings, and clean and paint... You are at 1800-2k, without labor. The disc brake conversion with parking brake even with a diy kit adds up fast as well. This isn't an argument against, but just a confirmation that it is easy to spend a lot on a rear end that may not be exactly what you want, when trying to save a few bucks.

However,if you are looking at an off the shelf 9" with brakes- it gets up near $4k really fast.

I think the days of finding a good 5 lug with posi in the junkyard or on Craigslist for $200 are long gone unfortunately. People are hoarding parts.

Re: Rebuild 12 bolt or swap to 9 inch?
 

Thanks for the confirmation that I’m not way off the mark on pricing. You’re right about Truetrac/Limited Slip/Posi units being expensive. That plus the 5 lug axle swap, and new ring and pinion gets expensive quickly. The shop (L&R Transmission in Clemmons, NC for any locals on here) is very reputable, and proposed cleaning/painting the housing, replace all seals, bearings, etc. I honestly don’t remember the exact price, I last talked to them in May. It was in that ballpark. I’ll still be on the hook for brakes, but everything else will be new. I think I’m still leaning towards having the 12 bolt rebuilt, but you look at the cost and start wondering if buying all new wouldn’t be better.

Re: Rebuild 12 bolt or swap to 9 inch?
 

I’ve been doing my homework on it. I don’t farm out much work, but I don’t know anything about the dark arts of properly setting up a rear end. As far as the disc vs drum question, drums are fine, but due to the axle swap, I have to buy everything anyway. Seems like I may as well spend a little more now and go ahead with discs. My philosophy on this truck is that I’m only doing something once. I’m going to spend the money now to get the long term result, and not have to go back and redo anything that I don’t have to. The first build on this one is basically everything but body work. I’m building it for a 16 year old to drive, so it will get scratched or dinged. Once he gets older (after college or beyond), we can take it down and do the body work. Everything underneath should still be good. I’m just building with an eye to the future.

Re: Rebuild 12 bolt or swap to 9 inch?
 

No mention has been made of the newer Ford 8.8" that seems to be quite popular for swaps and it could already have the disc brakes and maybe posi too.

I guess it depends where you are. I've had a 64 diff on Kijiji for probably a year now and nobody wants it. No posi though.

Re: Rebuild 12 bolt or swap to 9 inch?
 

I would like to hear about other options. In my research, it doesn't seem like it really matters that much (cost-wise) where you start with regards to the axle housing except for matching the wms width.

I am unaware of a stock axle housing (14 bolt, 9", 8.8") that is similar/same, without going down the rabbit hole of looking for a relatively rare combo of vehicle. For example a late model 14 bolt out of a cab and chassis dually.

Once you are having to narrow and buy custom 5x5 axles, and discs; how much would you think you would save? Honest question, out of my own ignorance.

Re: Rebuild 12 bolt or swap to 9 inch?
 

lock-right or power-trax . 2 top brands .

they replace the oped spider gears of the 1 wheel burn and give you a mini mech locker unit like a detroit locker works .

i have one for sale in the 73-87 section of parts for sale . it fits the 28 spline 10 bolt pickup axle .

Re: Rebuild 12 bolt or swap to 9 inch?
 

another option for people is 6 lug front rotors they do make and then no mods to the rear 6 bolt axles .

and when i was doing wheels for people years ago i always liked a 6 lug rim look better of the 5 lug . it was the way the design layed out better on 6 lug .

also tons and tons of 6 lug out there now with all the imports and gm have gone 6 lug on 2wd .

Re: Rebuild 12 bolt or swap to 9 inch?
 

One thing not mentioned - they require no specialized tools or knowledge to install.

Re: Rebuild 12 bolt or swap to 9 inch?
 

For that kind of change i would look at a dana 60 SRW from a 2000ish 2500 light duty. Stout axle with a chunk that will take alot of abuse. Also comes with rear disc. It would be 6 lug though

Re: Rebuild 12 bolt or swap to 9 inch?
 

Seems a bit high. My brother had his 12 bolt rebuilt with a True Trac, Yukon Gears and narrowed Moser axles. He spent about $1100 in parts. I plan on doing the same next year. I'd do some more shopping around.

Re: Rebuild 12 bolt or swap to 9 inch?
 

I wasn’t aware of the lunch box locker. I may do some more research on that. I could still do the 5 lug conversion (I’m already pretty locked into 5 lug, so it’s now a given). If my ring and pinion look decent, I could pick up some 5 lug axles that match the stock spline count, replace the axle seals at the same time, and potentially be out less coin. I’ll have to give that some thought and some research. Thanks for the input guys, keep the suggestions coming!

Re: Rebuild 12 bolt or swap to 9 inch?
 

Do the lunch box lockers act like a welded diff, or do they allow some speed difference of the axles while turning?

Re: Rebuild 12 bolt or swap to 9 inch?
 

there a ratcheting design for street use .

my trucks are 1ton 4x4 stuff and or my 1 2wd is a detroit true trac posi . so my axles have lockers or the gm gov-loc units . my feedback for road use wouldnt help you on the lunch box unit . but i know lots of guys run them and seem to be happy .

Re: Rebuild 12 bolt or swap to 9 inch?
 

I called my powder coat/blasting guy today because he has a bunch of local contacts. He’s putting me in touch with a local guy who owns a shop, and does a lot of rear end build on the side for his personal pro mod, and for others in the area. Hopefully I’ll get a better idea on pricing from this guy. I will post back with any progress.

Re: Rebuild 12 bolt or swap to 9 inch?
 

Your '64 12 bolt will have 17 spline axles. All the 5 x 5 conversion axles are 30 spline. I believe most if not all 'lunch box' lockers for a truck 12 bolt will be 30 spline.

Re: Rebuild 12 bolt or swap to 9 inch?
 

CaptainFab,
What is your idea of the limits of a truck 12 bolt, power wise??? Just wondering...

I talked to the owner of the "Farm Truck", years ago before they all became movie stars.
His pickup had run a best of 10.13 quarter mile pass, been years ago...Right up until they got their TV deal going the Farmtruck ran a TH350 trans...my jaw dropped, when he told me. The last time I talked to him he had just switched to a TH400, just for peace of mind, no other particular reason, out of Shawn's mouth...I am pretty sure the 10.13 pass was way before he upped the cubes in his engine.
The Farmtruck has always had a 2 piece drive shaft,and a 9" ford differential, (when I sw it run...) I have no idea about what he has run for drive train in recent few years (hollywood years...LOL)

Re: Rebuild 12 bolt or swap to 9 inch?
 

What is shops name in clemmons? I live in lewisville NC and also do repairs but nothing like that I probably gonna need rear end work on my 71

Re: Rebuild 12 bolt or swap to 9 inch?
 

Thanks all for the input, it is much appreciated. After looking at options, I think I’m going to go with the shop that originally quoted me. They have a great reputation, and there’s something to be said about dropping the rear end off, and picking it up completely done, cleaned and painted. I’m all about doing it myself, but I have to remember that I still have an entire truck to build. Captainfab, I’ll PM you, but I’m going with your Camaro brackets. Impala/Caprice rotors with a caliper that had an integrated parking brake? Sign me up!

Re: Rebuild 12 bolt or swap to 9 inch?
 

The strength limit of any differential is going to be directly related to the tires bolted to the axles. Also there is the variable whether you are talking a completely stock truck 12 bolt, or one that has been built to withstand abuse. With that said, my son had a '79 K10 with a mildly built SB400 and on 36" tires. He broke the axle tubes loose from the center section and spun it 90*. I will add that my son used to be really hard on his vehicles, so this would not be typical of most people. He could have probably broke a nerf ball if he tried. A truck 12 bolt under that same truck with say 31/10.50 tires would last a long time. The same analogy could be applied to street use.