Converting 63 12 bolt rear diff with 6 bolt to 5 bolt,

[russellrox]

I have been researching this for a little bit, I read on here that you can remove the axles and drill them out to the 5 bolt pattern at a machine shop, what rear drum with 5 bolt would fit for this setup, or is it the same thing as say a 71 diff, I have access to a 71 5 bolt diff but read that it's a pita to change since you have to do lots of cutting. I know you can buy a changeover kit that gives you new spiders and axles but if I can drill my existing ones, I would much rather do that.

[Blu64c10]

Yes existing axles can be drilled, I drilled the axles on my 64 as seen on the top of page 2 in my build thread.

http://67-72chevytrucks.com/vboard/s...=642354&page=2

[Captainfab]

Yes your original '63 axles can be plugged and redrilled to the 5 x 5 wheel stud pattern. But I would only do that if the axle bearing surfaces are in excellent condition. Yes you can use any '71 and up 5 x 5 brake drum as long as it is for the 2" wide shoes. If you have access to a '71 12 bolt from a C10. that will bolt right under your '63 as long as both are the same type suspension. The one thing that will be different is the panhard bar and it's mount on the frame. You can use the '71 panhard bar if you put a slight bend in the end that attaches to the frame bracket.

Otherwise you will be left with buying the 30 spline aftermarket 5 x 5 conversion axles and the corresponding spider gears.

[russellrox]

I found a 71 12 bolt rear diff, 100.00 for the whole thing, has coil spring rears, read on here that the diff is a bit wider, and the trailing arm mounts are in a different location and would have to cut and weld to make it work, on top of moving the panhard bar location. Wondering if its less trouble to just bite it and switch the axles and spiders.

Originally Posted by Captainfab

Yes your original '63 axles can be plugged and redrilled to the 5 x 5 wheel stud pattern. But I would only do that if the axle bearing surfaces are in excellent condition. Yes you can use any '71 and up 5 x 5 brake drum as long as it is for the 2" wide shoes. If you have access to a '71 12 bolt from a C10. that will bolt right under your '63 as long as both are the same type suspension. The one thing that will be different is the panhard bar and it's mount on the frame. You can use the '71 panhard bar if you put a slight bend in the end that attaches to the frame bracket.

Otherwise you will be left with buying the 30 spline aftermarket 5 x 5 conversion axles and the corresponding spider gears.

[Clyde65]

No, use the 71/72 coil rear. It's a bolt in AND you have the opportunity to rebuild and upgrade the 12 bolt.

[frankslagoon]

another problem with the 63 rear end is the backing plates are pressed on and it's hard to find rear disk mounting plates if ya ever decide to go there. I used a 66 burb rear end and it fell right end. So can anyone comment on trailing arm mount position between long bed and short bed. I thought they were the same. seems like the 71 would be the way to go there is only like a 1.5 " differents in total width . measure twice - buy once.

[russellrox]

so the trailing arms bolt right on without modification other than the panhard bar, I'm fine with relocating that, but do not want to mess with pinion angles and relocating the main trailing arm brackets, like you said, I only want to buy once.

[russellrox]

got the box off today and got to get a real good look at the diff, noticed the backing plates on the diff have 4 bolts holding them on, did any of the 63's come with an early 64 diff that had the bolt on backing plates, unless it has been swapped out previously. the panhard bar mounts on the rh axle tub about half way to the wheel, and goes up to frame if that helps identify this at all.

[Clyde65]

60-62 are the only trailing arm mounts that are different, they are a slight different angle than 63-72 mounts are.

[frankslagoon]

So I could be wrong about all the 63 's being press on backing plates. the panhead bar on the 63 rear end is welded on the right axle housing like ya said. the 66 and my 70 are right close to the carrier ass. actually part of the casting I think.

[Captainfab]

The original '63 12 bolts had the backing plates pressed on. It is possible that your differential is a late '63 or it has been changed sometime in the past 52 years. The '63 and '64 12 bolts had the panhard bar mount welded to the passenger side axle tube. The '65-'72 12 bolts have a boss cast into the center section where a stud is bolted in which receives the end of the panhard bar. Consequently the bracket on the frame is at a slightly different angle. The trailing arm mounts on the '63-'72 12 bolts are at exactly the same distance apart. As Clyde65 said, it is the '60-'62's that are different.