My90Iroc

Basically exactly what is says in the topic, what's involved to swap out a 10 bolt drum rear and put in a 9 bolt disc rear? What parts do I need, what problems should I expect, and what advice do you have? Thanks a lot.

MRZ28HO

I am not to familiar with the caliper options on 9-bolts, but do know they had the offset style. I have a 10-bolt with the same caliper arrangement, here is what I went through.

You need:
New parking brake cables (the OEMs might be worn, might as well change them)
Make sure the hard brake lines are on the differential. One the driver's side it uses a hard line to the caliper.

And that is it. If you want to go all out, you can replace the prop valve with a disc rear prop valve. I have seen cases (cars in person) were it is not needed.

SSkindog

I am doing it right now in my 88 Bird. Ordered a Moser 9 inch bolt in housing. One can choose the housing ends that one wants. I made the mistake of choosing 94 - up Camaro rear disc housing ends, thinking I could pick up parts in the boneyard. NOT!

So, I woulda been better off with the ford housing ends, and bought an aftermarket Wilwood disc brake set up.

Damon

Having not done this EXACT swap, I'll give some general info.

Aside from the misc. parts you need a master cylinder from a same-year 9-bolt 4 wheel disc car and the proportioning valve.

Disc brakes work at different pressures and have different volume requirements than drum brakes. If you don't replace these parts you will likely end up with rear discs that either provide almost zero stopping power (in which case why did you go to discs in back anyway?) or lockup much too soon (dangerous).

The disc brake M/C should bolt right up since they used discs and drums out back that year depending on what options the car had. Ditto the proportioning valve.

MRZ28HO

I believe he is talking about the Australian GM 9-bolt differential (this diff. came on some 3rd gens stock), and not the "Ford" 9 inch differential (aftermarket).

TheGreatJ

If you get a J65 prop valve from the same year as your car (NOT your new 9-bolt) then you don't have to change the master cylinder. The prop valve handles all pressure and flow modifications. If you don't change the prop valve your brakes will still work, but the rear discs will provide very little stopping power. Which means brakestands will be easier, but stopping will be harder. Personally I like being able to stop...you can always get a line lock for brakestands.

If you get the e-brake cables and brake lines with the 9-bolt it's a direct bolt in.

88 427 Camaro

The housings (with brakes) are directly interchangeable. I did the swap about 4 years ago. I installed the master cylinder from the donor 9 bolt car. I had to get an adapter fitting to connect the hard line on the car to the rubber hose on the rear. I used the brakes from the 9 bolt. Straight forward swap. (I did not install the ebrake stuff though).

More info on my car is at www.koolmeister.com and more info and parts for 9 bolts is at www.9bolt.com

Miles
Diff Solutions
www.9bolt.com

My90Iroc

Thanks for the info. Is 9bolt.com the only place to buy parts for these rears or what, I didn't see anything in Jeg's for the 9 bolt? Thanks again.

87DJP2001

Just completed that swap last year. Replaced a 10-bolt drum with a 1989 BW 9-bolt disc on my 1987 IROC. Pretty straight forward, one for the other. Only items need were the Proportioning Valve, Parking brake cables and new fittings for brake lines( SAE/Metric) thats it. Then your normal maintance items.