will the disk brakes on a 9 B/W bolt just simply swap over to a 10 bolt without any problms or are the axle housing ends setup diff. my 10 bolt has drums and my 9 bolt has disks.

 

No you have have modify you axle flanges and you will need 10 bolt backing plates.

 

Transam84,

You are sitting on a very appealing and highly wanted factory 9bolt DISC BRAKE rear end. 9-bolts are always in demand and are not very often fitted with the stock disc brake assembies, alot if not most were drum brakes.

To the person that wants to keep their thrid gen fitted with the best original factory options, you are sitting on a gold mine. I would srtongly suggest you have it rebuilt and keep it if you are into original looks (original meaning not going to aftermarket like Moser 12bolts, or Currie 9" rearends that are no longer nostalgic)

If not worried about staying original with brakes ect, then just know what you have is fairly sought after and command a decent price on the market.

 

I have to disagree with that.....

Virtually ALL 9-bolts that were installed in these cars came with disc brakes. Somebody actually posted a pic of a drum brake one once, just to show that such a thing existed, I think he's the only one that's ever claimed to have that.

There are 2 disc brake systems that came on 9-bolts; the 88-back cast-iron Saginaw caliper system, and the 89-ONLY aluminum caliper PBR system. The correct answer to your question depends on which brake system you have.

9-bolts also came with a number of ratios. The majority of them were 2.77 or 3.27. The 2.77s are near useless, because 3.08 is the highest gear you can put in one of them: nobody makes either a ring gear spacer, or the "special" gears, for the 9-bolt. 3-series carriers are hard to come by, by any method other than buying a rear and taking the carrier out to upgrade a 2-series rear. But, there's no real point in doing that, because if you buy a 3-series rear, it makes a whole lot more sense to just use it and throw the 2-series one away, than to take 2 rearrs apart, swap gears over, and then throw a whole bunch of disassembled parts away.

If your 9-bolt has the Saginaw brakes, I would not recommend doing the swap at all. They suck. They can be made to almost work as well as drums, by rebuilding the calipers, adding the caliper recall mod, and modding the prop valve. Still not a good candidate for a swap.

If your 9-bolt has the aluminum PBR calipers (not real likely but not impossible either), then those are excellent brakes, and are well worth the swap. On the other hand, if the 9-bolt is a 3-series one, it makes more sense to swap it in, than to futz around with graunching its brakes onto the 10-bolt; especially if your 10-bolt has anything less than 3.73s in it.

Disc brake rear end housing ends are quite a bit different from drum brake ones. But drum rears can usually be modified to accept discs; but not the other way around.

All in all, there's no one right answer to your question, without some more information.

 

RB, the why does it appear people around here asking every so often about installing disc brakes on their 9-bolts. That question comes up alot. It appears to me that the 9-bolt disbrake backing plate are rare from what I've read in various posts over the years?

Dean

 

Picture of 1989 9-bolt with 11.655 rotors and PBR Aluminum calipers.

 

I think they mean "real" disk brakes for the 9-bolt rear, not the OEM iron calipers and small rotors. That's exactly the situation I'm in now that I had to decide whether to replace those original weak parts or upgrade to larger rotors and PBR calipers. The backing plates for the PBR calipers are different than the plates used for the earlier iron calipers.

 

I've never seen a post about installing disc brakes on a 9-bolt, that I can recall. I've seen more than a few about upgrading from the Saginaw garbage to something that actually works; but not a drum-to-disc swap.

The thing that's hard to get, that people are always looking for, is the backing plates for PBR brakes on a 9-bolt. It's different from both the Saginaw 9-bolt plate and the PBR 10-bolt one. And, they've been discontinued by GM; so they're not getting any more commonplace.