Hello everyone,
Well I am gonna do a rear end swap on my 91 RS. I got this 88 IROC rear end with disc brakes. So I was reading the FAQ About 10 bolt rear ends right. I read that 82-88 use iron single piston Delco Moraine calipers with 10.5" rotors and 89-92 use alum single piston PBR calipers and 11.7" rotors. Can I just get the 89-92 brakes instead of the 88 iroc stuff. Another thing I need more explaining in is proportioning valve. Which one do I get from this site the 90-92 valve or the 82-89 valve http://www.flynbye.com/catalog/c1_p1.html. Does it really matter which one I use. How about the threads will 88 threads/lines work with my 91 thread/lines. And for my parking brake I will need to purchase the 88 cable right or will my 91 cable work. I know it might seem like I am asking for answers again that have been answered on here
https://www.thirdgen.org/forums/tran...-10-bolts.html
I just want to clear up confusions some more so please help me out.

Thanx,
Edgar

 

I did almost the exact same swap with my 91 RS, except I had a 9 bolt. Anyway, You MUST purchase and install the 1LE brake proportioning valve for the rear discs to work! The one you highlighted is the correct one to use. You can purchase it new or possibly find a good used one from a wrecking yard for about 1/2 - 1/3 of the price. However, a used unit must be harvested from a 90-92 disk braked 3rd gen. Personally, this is a no-brainer. New is the way to go.

The rear calipers can be purchased at most auto parts places. The iron units work okay, the parking brake system does not. Get a brick, stick under tire. Trust me. The aluminum units are preferred but more pricey.. Thing is, you'll need to know which one bolts to and fits the housing ends. What year is the donar rear end out of? Again, I'd suggest you check with the folks at flynbye to get you the right package deal. They can most likely set you up with the valve, calipers, and parking brake cables you'll need all at once.

Lastly, you'll probably run into issues with hooking up the parking brake cables to your parking brake lever. I did with my 91RS. To solve it, I went to the wrecking yard and got a later model parking brake lever assembly plus the metal bow tie that connects the cables under the car. That allowed me to have parking brake cable adjustment.

Good luck!

 

I work at O'reilly Autoparts and I was comparing part #s on the calipers from a 88 IROC and a 91 Z28 the aluminum calipers for both are the same so would that mean they will bolt on fine or still check first. The rotors were different part #s though there will probably be fitting problems right there am I right or wrong. I would assume that the calipers are shaped differently because of rotors. Hopefully they are in stock at my store to compare them. The rear end is from a 88 IROC. How about for your hose lines did you get 90-92 lines, the hose lines from the donor rear end were ruined.

Well thank you so much for the clearing up of things .

 

I purchased new soft and stainless hard lines from Classic Industries. Of course, those can be purchased eleswhere.. but, the set up is the same for your car as it would be for the donar IROC. The t-fitting just needs to couple to your RS's and it will. As for the rotors, I'd go with the standard discs that match the calipers you select to use.

 

Oh alright sounds good. Thanks once again .

 

Anytime.

Have fun and good luck!

 

BTW, might consider replacing the soft IROC lines and your front soft lines with braided SS lines, fore and aft. Got to bleed the system anyway.. and you'll have better pedal when done. Just for your consideration.

W

 

Yea I am gonna have some fun with this. As soon as i get everything and start on it. Yea I am thinking of getting the braided lines they have on flynbye.com too and ill just buy hard lines from work and do it myself. Will see what happens as I get the parts.


Oh they have a kit for the lines ill just go with that.

 

Ed Miller fabs a kit that allows you to bolt on larger rotors and PBR's to a drum rear. See the link below. In many ways this option, if you're satisfied with your current gearing, is a good one. No problems with speedo drive and/or driven gears either.

http://www.flynbye.com/catalog/i30.html

Since you have a 91, you'll need the second design valve so that the thread pitch will match you car.

http://www.flynbye.com/catalog/i172.html

You'll need the second-designed parking brake cables which are designed for rear discs.

Swapping in the 88 rear would be a step backwards, I think: smaller rotors, iron Delco-Moraine calipers, and 26-spline axles.

JamesC

 

The front calipers no doubt have the same part number as all 82-92 cars, with the exception of the 1LE cars, have them. The rears 89-92 will have different part number from the 82-88 models.

JamesC

 

Well its not really a step backwards to me because I am gonna replace a non posi rear with a posi rear with rear disc brakes which is better than drums. I would really like to get those bigger brakes but will do it later on. I plan getting the 90-92 prop valve and the brake hoses. For the parking brake cable we should stock it at my job hopefully.

 

Make sure the limited slip functions as designed before you think it's a cost-effective upgrade. Good luck on your project.

JamesC

 

Does flynbye.com sell brackets for the rear I got to fit in the PBRs. If I buy the brackets they sell to convert drum to disc, will they bolt on to the 88 rear end. But idk I think it would be better to atleast have disc prop valve then a drum prop valve. The rear is good took it in to my transmission and differential class so my teacher can see it. Thanx for all your info it helped alot more .

 

The above kit is to convert drums to discs (PBR's), which is what you could do with the 91--I'm assuming it has drums anyway.

If you want to convert the rear discs on the 88 to PBR's, you can do that too:

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

BTW, where the combination valves are concerned, there is an increasing bias from drum to standard discs to PBR's.

JamesC

 

So from viewing link of your thread, from my understanding if I wanted to put PBR brakes on the 88 rear end, I need a backing plate right. Then everything else should be straight forward after right. The thing is will my braking be effected by having PBR brakes in the rear with a 1LE prop valve and then standard disc in the front. Man this is hard lol im undecided on what to do now.

 

You need the backing plates (and shims probably) and everything else is straightforward, though of course you'll have to pull the axles. The so-called 1LE combination valve is correct. With the exception of true 1LE cars, which were cars with dual piston alum calipers up front and PBR's out back, all J65 89-92 cars were equipped with standard discs on the front and PBR's on the rear.

JamesC