I have a 1987 9 bolt with the cast iron discs, plus a spare 1991 10 bolt with drums, and have several questions. I ran a few searches but most posts centered (understandably) around swapping from drum to disc on 10 bolts, or early disc to later disc for both 9 & ten bolts. I'm guessing 9 bolt/drum axles are very uncommon--otherwise had I found an article on swapping drum to disc on a 9 bolt I could have looked into reveresing the procedure. My goal is to have reliable functional rear brakes (and I'd like to keep it inexpensive; if I could afford it I'd get AndyZ28's kit)--I've had 3 third gen drivers and am satisfied with having rear drums--what mods would I have to do to put drums on the 9 bolt? Can I use the drum parts on the 10 bolt that I have? I read about how crappy the early discs are and I am afraid of the hassle. Any one out there with good experience with their early rear discs (can they be made to work properly)? I know there aren't too many fans of drum brakes, but I can't afford to do the glamorous upgrade right now.

One more thing--for future reference (i.e. when I will be able to afford the glamorous upgrade), are '93-97 rear discs just like the 89-92's (curious to know any significant differences that would affect swapability).

Thanks much!

 

Switching to drum brakes wouldn't be a good move IMHO. You'll have to pull the axles so you can swap backing plates, PLUS the 10 bolt plates will need to be drilled to fit your 9 bolt. At that point you'd be better of swapping on Andy's kit or 4th gen rear discs since you'll need to do the same procedures. The early rear disc brakes aren't great, but they will work fine.

The biggest thing you need to do with the early rear discs is use the parking brake everytime you park the car. This keeps the rear brakes working properly AND keeps them adjusted properly. Once I got in the habit of using my parking brake, my rear brakes worked better.

Some people however, do have some trouble with thier early style rear discs. There is a kit available from GM to solve this problem. Others have even done a simple and inexpensive mod to their proportioning valve to increase the presure to the rear brakes. So far, there seeems to be no ill effects caused by doing this mod. Check out this thread: https://www.thirdgen.org/techbb2/sho...hreadid=127100

As for the '93-97 rear discs, they are not "just like" the '82-'92. They will however bolt onto your axle with some modifications as I mentioned above.

I hope this helps you out.

 

Thank you, it does help. I'm glad to hear reassurance on using the older style. I looked at both axles when I got home today and it is in no way worth the effort to try to put the 10 bolt drums on the 9 bolt axle--the backing plates are COMPLETELY different. I will definitely either be doing the mod described in the above link or just getting the Wildwood adjustable proportioning valve to replace the factory piece and go for some custom tuning. I also will use the parking brake all the time as the car this will go in is currently a 5 speed. Couple more questions:

I've seen this addressed previously, I just can't find it again--can someone give a quick rundown (or link to were it is) of the actual shortcoming of the cast iron caliper and how the GM kit addresses the problem?

Is the GM kit a rebuild kit that needs to be performed at every brake job or is it a one time mod to the caliper independent of a brake job?

Is it still available through GM?

I don't have mucho cash, otherwise I'd just get the PBR's--however, some of the stuff I've seen on these boards are horror stories (thats how they sound anyways) of how people have spent close to the cost of a PBR kit fooling with the iron calipers.

please pardon my ignorance

Thanks in advance

 

It's a one time rebuild thing and yes, GM still has them. Search for user "Apeiron". He listed the part numbers a while back and may still have a kit lying around.

FWIW, I'd just upgrade your 9 bolt to PBRs and be done with it. You can piece it together over a little time for not a lot of $$$..


HTH...Ed