Picture of 1989 9-bolt rear PBR set-up. And NO and again NO you can not make a 9-Bolt into a 10-bolt.

It's all different, mounting plates,calipers,e-brake cables & rotors.

The Delco calipers are a single piston, steel design and are prone to sticking or just plain not working properly. The Delco design also uses a 10.5" rotor. The PBR calipers are a much better single piston, aluminum design and use a 12" rotor.

If you have a 9-bolt rear end you'll have some trouble bolting on the PBR calipers. The only F-bodies that used the 9-bolt rear w/ PBR brakes were the '89 models equipped with rear disc brakes. Since this was a limited production the correct backing plates have long been bought up and are no longer available in GM's inventory. Some people on this board have made their own brackets though.

Starting in '90, GM dropped the 9-bolt and all F-bodies used a 10-bolt rear end. The rear disc brake equipped cars all got the PBR design brakes.

The 9-bolt rear end is better, but aftermarket parts are limited and they tend to be very expensive. This is why many people prefer the 10-bolt - the parts are readily available and affordable.

Josh, here's a pic of the Moraine calipers. This was a shot of my '88 rearend brakes:

Here's a shot of my "new" '89 model PBR brakes after I swapped. These give you a bigger 12" rotor and calipers that WORK!!


Ed

The swap isn't that hard. You'll need 9 bolt backing plates, different axle brake hard lines, and different e-brake cables, and of course the brakes.

You can find it all if you know where to look...

Ed

I just got through swapping a 9 bolt rear into my car and I also swapped the Delco Moraine brakes for the PBRs prior to installing it. Well worth it.

There's only one thing different:


Everything.


And I do mean everything. Every single piece. The lines, brackets, hardware, the calipers themselves of course, the pads, the backing plates, the caliper carriers (which the iron caliper brakes don't have), parking brake cables and brackets, every single piece. Every single piece is different. Name a piece, it's different.

But like eb said, the flange on the rear is the same, so all you have to do is find a complete PBR setup for the rear end you have (9-bolt or 10-bolt) and it will bolt right up to a Saginaw brake rear of the same type. That is, 10-bolt parts won't bolt to a 9-bolt or vice-versa, unless you have the right backing plates for your rear. The PBR backing plates for 9-bolts are quite difficult to find, since they were only offered for one year, and GM has long since run out of them.

The 9 bolt will fit any F body that the 10 bolt will. All the mounts and attachments are the same. As for clearing 15" rims I'm not sure. There is a real possibility since the rotor is 12" in diameter and with the caliper mounted it would be tight at the very least. As for being an auto that doesn't matter. My car is an auto and it now has a 9 bolt. As for 89 being the last year I'm not so sure. The 90 model GM Firebird service manual has a section on the Borg Warner 9 bolt so it appears to have been available on 90 models to some degree. Possibly they just put them in cars until they ran out. As for a 9 bolt with PBR brakes being a good idea just ask if anyone would be willing to switch back to the Delco Moraine brakes or drums. I know I wouldn't.

They came with 15" rims from the factory.

Are there any offset problem with the 12" PBR set-up? I do not want by back wheels any closer to the fender. I think I will try this on my 86 as the brakes (disc) are boring compared to 2000 Grand Prix. ebmiller88 is this a hard conversion, how long does it take, is there any fabrication involved. I noticed that third gen resource has the calpier brackets calipers and discs so all I need is the parking brake cable and the brake lines right?

The actual size of the PBR brake rotor is 11.655" NOT 12" as people tend to round numbers up.

No offset problems here and I'm using front wheels at all 4 corners. I switched from drums to discs so the slim spacer that was used on the drums was ditched during the swap.

Well, even in good working order the Delco brakes stills are not as good as the PBR brakes. The bigger rotor with the PBR brakes gives you better braking ability

Also, even with an auto trans you should always use the E-brake when you park the car. This does two things - 1) It helps keep the rear brakes in good working order and 2) It keeps the rear brakes properly adjusted.

That could be a long wait. You could probably find one if you look hard enough, but if it needed new gears it could get expensive.

The 10-bolt posi PBR rear is probably your best bet. The 10-bolts are common and new gears and such are easy to come by and won't break the bank.

You won't actually notice a difference between the two while driving. I check the classifieds board every morning and saw a couple of disc brake rears for sale just today. One was a 10 bolt with 3.23 gears and I think the price was around 3-400$ complete. The 9 bolt is stronger by virtue of it's larger ring gear and by it having a 4 pinion posi instead of the 2 pinion found in 10 bolts. Another feature is the fact that the axles are held in by retaining plates on the 9 while 10 bolt axles are held in with c clips. When I swapped rears it was mainly for disc brakes out back and for a better gear ratio,the fact that I wound up with a 9 bolt is a bonus in my opinion.

I've just completed a complete rebuild (without changing gears) on my BW 9-bolt and it cost about $430.00 without the brakes being swapped! For the brakes I shelled-out another $510.00 for all-new parts. It's a marginally stronger rear-end and is legal for NHRA racing due to the bearing retainer, but If I did it again I'd spend the extra dough for an 8.5" conversion rear-end.

The 3.73 gear is a great around town gear. 4.10s would just be way too much for the LO3. I went from a 3.73 10 bolt to a 2.77 9 bolt because I was sick and tired of the 3.73s. They were great up to 60mph/2000rpm but try and keep up with traffic on the interstate and you're turning almost 3000 rpm in OD-not good in my opinion. Just my opinion,try for 3.45 with the auto. It'll be a good middle of the road gear and should provide a good take-off and still keep the revs down to a decent level during cruising.

I sure wouldn't go with that low a gear. Go with 3.23s (3.27s) or 3.42s (3.45s), other wise you won't get crap for mileage. I get 25+ MPG in my Iroc with 2.77s and I still have plenty of torque.


Ed

The correct gear is the one that puts the engine at its peak efficiency under the conditions it most normally operates in. If you have a motor with lots of low end and no top end whatsoever, such as a TPI motor or a stock L03 or LG4 motor, you need to keep the engine RPM down in the range where that particular combo is most happy. On the other hand, if you have a carb or aftermarket FI setup that alows the engine to produce meaningful power at some higher RPM than a stock one, you might benefit from a higher gear ratio.

For example, a stock L69 came with 3.73 gears, because that puts the engine RPM into the range that that particular engine works best in, for a typical mix of city and highway driving. Even the factory thought so. On the other hand, a TPI motor will work best with 3.23 gears if stock or possibly 3.42 if it's modified or if it's one of the later model better flowing ones; 3.73s may actually slow the car down compared to the lower ratios, because it forces the engine RPMs into a range where it has less power and effifiency.

If you've got a stock L03, 3.73s are too much. 3.23 or 3.42 would be better. On the other hand, if it's modded or you plan (seriously plan, not just spank off about "someday I'm going to put in a twin-turbo LT5") to mod it, 3.73s are usually about the best overall choice for a 700 or T-5 car. 4.10s might be better for a T-56 car with its taller overdrive.

I definately agree here. I too couldn't decide what rear to get. Really wanted the 9 bolt with PBR's but its scarcity and cost efficiency did not make it seem worth it. Finally, after breaking some teeth off my ring and pinion gears, I was forced to make a split decision or pay $500+ for rebuilding the crappy drum rear. If youve been looking into getting aftermarket wheels and don't mind diving into an investment, I would suggest a 93-97 10 bolt, as they also come equipped with PBR'S and are relatively plentiful. I picked up a 95 Z28 rear with 3.23's and posi for $250 and saved myself $150 in not having to get adapters in the back, so the way I see it I paid $100 for the COMPLETE rear. Take everything into consideration, but I've always thoughts the best decisions usually come when under pressure Good luck, Efrain.

If you wanna keep the wheels you have, then a fourth gen rear is not for you. It requires that you get different wheels with different offsets(backspacing) than the ones that came on the thirdgens cause the 4th gens rear are two inches wider on each side. I just wanted to put another alternative for you out there, what worked for me might not work for everyone. To learn more about backspacing...look here http://www.skulte.com/adapterfaq.html