LS1 rear brakes swap onto Pontiac

[jrsstoy]

I’ve searched the web for a few days now without success. I wanted to know if anyone has done the rear LS1 brake swap onto a 1969 Firebird. I currently have Wilwoods disc brakes in the front and drums in the rear. I already have the rear LS1 brakes with parking brakes and wanted to know what is needed to complete the swap onto the Pontiac 10 bolt rear end since the axles are different from the GM 10 bolt c clip axles. I know that the GM axles require a spacer that is sold by BRP and I have seen many example of the swap on the Camaro’s but can’t find one for the Firebirds .if some could please guide me on the right direction, it would be really appreciated.

[79 Camaro]

Don't know if I can help but I will give it a shot. I think the only way you are going to know is if you pull the stock drum brakes and backing plates and then pull the axles. I had a 68 Firebird with the stock 8.2 Pontiac rear end. IIRC the axles are held in by the axle bearing plate not c-clips like a Camaro 8.5. I could be wrong its been many years since I built that 68.
So after pulling the axles get the LS1 backing plates bolted on (if it fits) or mod as needed. Reinstall axles and then bolt on the discs and see how they line up with the calipers bolted on. Just .02 hope it helps.

[cdrod]

The original pontiac rear will NOT have c-clips; if it's the original rear it will have bolt-in axles. The LS backing plates & calipers will bolt right up, but you will need a bearing spacer to hold the bearings in place behind the axle retaining plate. I did a mock-up of the LS rear discs on a '72 Olds A-body (which also has bolt-in axles) and the LS backing plates are about 3/8" thick whereas the stock drum backing plates are about 1/16". I think the early firebirds have a staggered shock set-up in the rear, so you may also have clocking issues with the calipers because the LS calipers both mount rearward (RH=9 o'clock position; LH=3 o'clock position). The parking brake cables for the drum-in-hat shoe both pull forward but you will need to fabricate cable mount as this is not cast into the LS backing plate.
I ultimately decided to sell my LS set-up and I used a very similar rear disc set-up from a 2001 Blazer 2WD. It's almost exactly the same as the LS but the parking brake cable mounts are cast into the backing plates, the caliper pistons are 48mm (LS are 45mm) and the rotors are 11.61"dia (LS is 12.1" dia). At the time I was trying to fit inside stock 15" rims. Like all good projects, mine eventually morphed into 18" aftermarket rims and the 12" LS rotors would have looked better inside the larger rims.

Rodney

Here's a couple of pics:

[jrsstoy]

Thanks for your reply’s.

I found out that in fact my Firebird does have the stock bolt in axles. I went ahead and bolted up the LS1 rear backing plates and bolted them down with the axle retaining plate. Everything bolted up nice and easily but the axle had tons of play in it. I can see this is because of the difference in thickness between the stock drum backing plate and the LS1 backing plate. I never even knew there was bearing spacer. So I believe this bearing spacer would solve the axle play. So thanks for that great idea cdrod. I’m assuming that the spacer on your post was 3/8 thick.

[cdrod]

My bearing spacer was 1/2" thick (with the Blazer set-up), but you should measure your parts and fabricate to fit your situation. You don't want the bearings to be too tight, but not too loose either. I bought a small piece of 1/2" 6061 aluminum and had local machine shop make 2 donuts and then cut them in half. It was a bit tricky to install them behind the axle retainer, but not impossible. The bearings and axle seals need to be installed first with the bearing spacer last pressed up against the retaining plate.

[jrsstoy]

Finished my swap a week ago and the small challenge was well worth the result I got from the. Brake swap. If knew how much of a difference the disc to drum swap was going to be I would have done it years ago. The car brakes feel like might and day, brake pedal feel is great and the confidence I gained from driving my car faster is priceless.

[bukemoto]

Did you use the right and left backing plates or did you use 2 left side backing plates for the staggered shocks?