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Rear End Swap From Limited Slip Drums To Posi Disc

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Rear End Swap From Limited Slip Drums To Posi Disc

Old 01-08-2006, 10:42 PM
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Rear End Swap From Limited Slip Drums To Posi Disc

Hye guys i just want 2 know what all am i goin 2 need i think the guy if just giving me the Rear end but it has dics and is posi but i need 2 know what else i need i know i need a protioning Valve but where is that on my can know its an 89 RS with drums and if i can change it without removing the master cylinder can i get one of those adjustable ones from summit or what not ok what else ?? plz help me out
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Old 01-09-2006, 11:29 AM
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You will probably need some punctuation. You won't need to remove the master cylinder, just change the proportional valve depending on what type of disc brakes. You might need other things, but it is impossible to tell based on your post.
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Old 01-13-2006, 05:58 AM
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I fear to see how bad his other 6 posts are. There's a prop valve already in the line on a stock setup? I'm going to a 4th gen rear end this summer and am going to need a prop valve, I was thinking of putting it right off the master cyl which I have yet hear if it's a good idea or not. If there is already one in the line where is it located? I don't remember seeing anything in the rear brake line the numerous times I've been under the car but then again I wasn't looking for it and don't know what it would look like anyways.
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Old 01-13-2006, 03:11 PM
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Rear Disc Swap

Maybe I can help IronJuggalo communicating his question. Especially since I am looking for the identical information. I too have a 1989 RS with a drum rear axle. I would assume that he is getting a Non-1LE 3rd Gen F-Body Rear Axle with Limited Slip Differential and Rear Disc brakes. How many different 3rd Gen Disc Brake Rear Axles are there? Are some better than others? I seem to recall reading somewhere in this topic that the 1988? or 1989 and up set-ups were better. Does the proportioning valve need to be added/changed for the rear drum cars? Any other changes for this conversion or does it otherwise simply bolt up? Thanks in advance, 89MOCROC
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Old 01-13-2006, 03:16 PM
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Re: Rear Disc Swap

Originally posted by 89MOCROC
Maybe I can help IronJuggalo communicating his question. Especially since I am looking for the identical information. I too have a 1989 RS with a drum rear axle. I would assume that he is getting a Non-1LE 3rd Gen F-Body Rear Axle with Limited Slip Differential and Rear Disc brakes. How many different 3rd Gen Disc Brake Rear Axles are there? Are some better than others? I seem to recall reading somewhere in this topic that the 1988? or 1989 and up set-ups were better. Does the proportioning valve need to be added/changed for the rear drum cars? Any other changes for this conversion or does it otherwise simply bolt up? Thanks in advance, 89MOCROC
I shopuld imagine I'll have no wheel clearance issues since my car is equipped with 1985-1987 16" Iroc Wheels.
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Old 01-13-2006, 04:40 PM
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I wouldn't think so. I don't even know if you would need a prop valve, the only reason I need one is cause I'm going from a 3rd non posi drum rear axle to a 4th gen posi disc rear end.
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Old 01-31-2006, 10:20 PM
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is the posi disc brake rear end from a firebird the same as a 3rd gen camaro? I found one and was curious what kind of work would have to be done, considering is has disc brakes instead of the drums my camaro has.
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Old 02-01-2006, 10:38 AM
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Originally posted by 83Z28BlackBetty
is the posi disc brake rear end from a firebird the same as a 3rd gen camaro? I found one and was curious what kind of work would have to be done, considering is has disc brakes instead of the drums my camaro has.
1) Two types of rear axles used on 3rd gen cars. BW 9-bolt & 10-bolt. Nothing internal are interchangeable between the two.
2) All are Limited Slip RPO G80.Posi is a slang term for a Chevy Limited slip. However; the limited Slip on the 9 & 10 bolt are different types.

3) Up to 1989 all rear disc brakes had Iron Calipers & 10.5 dia rotors. 1989 and up had the PBR Aluminum Calipers & 11.688 dia rotors. This is for both the 9 & 10-bolt rears.
4) Best rear in my opinion would be the 1989 BW 9-Bolt with the 11.688 rotors. Picture of the 89 setup.
5) Going from a drum to disc set up in most cases just requires a New Proportioning Valve.
6) Again it depends on the rear axle, you may need new brake line fittings and parking brake cables & etc. Nothing real major they just bolt in with no structual changes for both Camaro/Firebirds.
Do a seach, tons of info on this common swap.






Last edited by DJP87Z28; 04-17-2006 at 01:26 PM.
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Old 02-06-2006, 12:56 PM
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what happens if you don't replace the prop valve? I just put the pbr's on my drum axle without changing anything else. Everything seems fine and the car stops way fast....
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Old 03-31-2019, 02:30 PM
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Re: Rear End Swap From Limited Slip Drums To Posi Disc

I have a strange situation on my disk rear end swap. The handbrake cable smacks in to the rear linkage and has bent the cable.
https://www.dropbox.com/s/yxy3nghj3b...20.45.jpg?dl=0

I am going to go under there with a hammer today and see if I can adjust the situation.
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Old 03-31-2019, 04:49 PM
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Re: Rear End Swap From Limited Slip Drums To Posi Disc

Place the hammer on the ground, and step away...

How low does the car sit? Because you should have a good few inches between the panhard mount and the brake cable. The springs and shocks that aren't shot should prevent the two from ever contacting each other.

Originally Posted by superccs View Post
I have a strange situation on my disk rear end swap. The handbrake cable smacks in to the rear linkage and has bent the cable.
https://www.dropbox.com/s/yxy3nghj3b...20.45.jpg?dl=0

I am going to go under there with a hammer today and see if I can adjust the situation.
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Old 03-31-2019, 10:39 PM
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Re: Rear End Swap From Limited Slip Drums To Posi Disc

That's the part that is strange, stock springs, was looking to put pro kit springs on there but this is just weird.

Originally Posted by Drew View Post
Place the hammer on the ground, and step away...

How low does the car sit? Because you should have a good few inches between the panhard mount and the brake cable. The springs and shocks that aren't shot should prevent the two from ever contacting each other.
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Old 03-31-2019, 10:59 PM
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Re: Rear End Swap From Limited Slip Drums To Posi Disc

It looks like something has shifted the position of the rear and I kinda'; doubt the hammer will fit it. Is the Track-bar & or the Pan-hard bar bent or twisted ??? It's also worth taking a good look at the rear trailing arms in case someone tried to use them as a jacking point and bent one of them.

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Old 05-10-2019, 11:10 AM
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Car: 1991 Camaro Z-28
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Re: Rear End Swap From Limited Slip Drums To Posi Disc

Anyone have steps/instructions on how to replace rear axle/diff assembly for a '91 Z including tools needed, etc.? Thank you!
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Old 05-10-2019, 11:35 AM
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Re: Rear End Swap From Limited Slip Drums To Posi Disc

Originally Posted by Blue1989RS View Post
what happens if you don't replace the prop valve? I just put the pbr's on my drum axle without changing anything else. Everything seems fine and the car stops way fast....
What happens is you’re begging for trouble. Disc brakes require dramatically different fluid volumes, and different pressures than what are needed for drums.

Not installing the proper proportioning valve when swapping from drum to disc, or disc to drum is an accident waiting to happen.
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