12 Bolt Differential build

GTR1999

Gearhead
Joined
Mar 24, 2008
Messages
435
Location
New Haven CT USA
Well I started gathering parts to build a 12-bolt, 373 diff for a fellow corvette buddy running 650+ hp.

I really like what I see so far, take a look at these baby's. You like to put your foot in it with a lot of HP, you may want to get one of these.


Here we have from L-R a 4 series case, new 12 bolt case and new 10 bolt case

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Here are the cross shafts from the 10 & 12 bolts

44910f3abdde76.jpg

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Going to use 10-17 spider, heat treated, 30 spline. I could also use the 17 spline stock axles but this 12 bolt is going all out.

44910f3a78393f.jpg


I'm also going to start machining the 10 bolt cases and fit the 12 bolt spider and cross shafts. For more strength for the 10 bolt blueprinted builds.
 
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Gary, Maybe a stupid question but I'll ask anyway. How is the 12 bolt housing mounted in a C3?
 
Just like a normal one but you have to clearance the lid and the case for the ring gear clearance.
 
TT is correct, the posi case is machined, the RG ground or purchased already done, the housing is ground to fit the posi case and RG. The steel cap is the same procedure as I already have outlined in the tech page. The principle is the same just a lot more work to fit and setup and they cost a lot more.
 
OK now (I think) I understand. The C3 housing and cover are used with the 12 bolt internals.
 
The more I get into this the more I find custom work is needed or parts need to be found. Due to the RG bearing a special grind the "stock" ARP or GM RG bolts are not going to work. I will need one off ARP bolts or use a hardened flat washer under the heads. The 30 spline axles are trick too.

I got in the 31 spline spindles and they are massive. I have to wait to post pictures because I can't get photobucket to upload? These spindles are one OD, not stepped like the stockers are. The bearings are different and one race alone is $45! This is from my personal supplier too.

I'll get the tools made up so the next ones will go better but it's a time consumer. I can't see how anyone is going to build these at home, too much fitting unless there is a machine shop nearby.

One problem is I now want this stuff for my cars, and I just rebuild all of mine!
 
All your pics don't work anymore. You can upload your pics straight to the vettemod image hosting service, no need to use photof*ckit :) Go to image hosting on top and upload your pics there.
 
OK lets try it TT.

Here is the 31 spline spindle. No step full diameter. I like this piece. I'll have to make a setup tool though.


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Here is the rest of the spindle kit

30490087bcbe8eb.jpg
 
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Yes, I have started to fit the steel cap and of course it has to be machined to be fit. I have the holes tapped and have to bore the cap to size. I will have to machine shims for both the pinion and case as well.

tapping1-2x13.jpg

capfittohousing.jpg
 
I fit the cap tonight. I have a few steel caps here and checked them all- all were different about 020" between them. I had to grind the pads flat and found this cap had 012 gap. Bored it to 0005 gap or 001"- "rock". I strongly suggest if anyone wants a steel cap, to have it fit by someone with a shop. I haven't had one yet that could have been fit at home with a file or hand grinder.
 
Worked on this some more, almost done just have to fit the cover. reviewing this job, I would not recommend someone doing this at home unless they have access to machine-tools. This job as a real PITA! Everything had to be fit and machined from the housing to the RG bolts this is not a bolt in rebuild.
I did revise the job to the way I build things but blasting,etching,POR15 and top coating as well as fitting a solid sleeve. The other rebuilders don't use a sleeve just loctite, I prefer the solid sleeve although it adds time and money to the job. I don't build things for time only quality.

Here is the sleeve used, same as a 10 bolt.

newsolidsleeve.jpg

grindingsleeveparalleandtosize.jpg

Billlet yoke has no sheild like the stock yokes do.

yokeinstalled.jpg

Richmond makes these gears and they're a PITA to setup. I had to machine shims.
finaldrive1.jpg

New Axles were painted and polished.

polishedjournals.jpg


C clips are used instead of snap rings. Much stronger but have to be fit.

cclips.jpg


Clip ground to size.

groundcclip.jpg

005 endplay set

005gap.jpg
 

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