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Drum to Disk Diff Swap

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Old May 18, 2017 | 04:24 PM
  #1  
Ja85z28's Avatar
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From: Mercedes, Texas
Engine: 305
Transmission: T5
Axle/Gears: 4:10
Drum to Disk Diff Swap

This weekend I am picking up a disc brake differential for my 85 Z28. After a thorough restoration, what problems am I going to face upon installation i.e....Emergency brake cable change or just adjust???? I have no idea what kind of problems are in-store???

Thank you in advance for your knowledge.

Respectful Regards
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Old May 18, 2017 | 05:51 PM
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LsxMatt's Avatar
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From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: Drum to Disk Diff Swap

Im not familar with the 3rd gen disk rears, as i went from a drum rear to a 4th gen rear. But you will most likley need to replace your proportioning valve with one from a disk rear, and also get parking brake cables from a disk brake car as well, but Im not 100% on this. Other than that, assuming its fully assembled with calipers, hoses and the hard brake lines, you should be good to go.
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Old May 18, 2017 | 07:08 PM
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Car: 1984 Camaro Berlinetta
Engine: LT1
Transmission: T56 6-speed
Axle/Gears: 4.11 LS1 Rear End
Re: Drum to Disk Diff Swap

The drum brake cables will not work,.... the cables you'll need will depend on the disk brakes your using. ( 82-88 disk, or 90-92 disk ?? ) If the rear is a LS1 rear-end ( brakes ) than there are a couple options to get the Parking brake working, but some custom work will be required.

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Old May 18, 2017 | 07:12 PM
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Ja85z28's Avatar
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From: Mercedes, Texas
Engine: 305
Transmission: T5
Axle/Gears: 4:10
Re: Drum to Disk Diff Swap

Thanks John. It's a 1984 Z28 HO. disk brake, posi, and 3:73 gears. Its been setting in dry storage under plastic for the last 10 years......lots of restoration ahead.
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Old May 18, 2017 | 08:45 PM
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Re: Drum to Disk Diff Swap

The disc brakes before 1989 arent even worth messing with. They wont brake as well as drums. GM issued tech notices and recalls, and finally went to Performance Brake Resources to supply a system that would work.
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Old May 19, 2017 | 01:03 AM
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Car: 1984 Camaro Berlinetta
Engine: LT1
Transmission: T56 6-speed
Axle/Gears: 4.11 LS1 Rear End
Re: Drum to Disk Diff Swap

Just seems like good timing; Send me a PM if your interested in an LS1 rear disc upgrade. ( I took these pics this afternoon while cleaning up in the garage a bit,.... )







P.S. Includes the LS disk E-Brake cables,too - just not pictured. Missing 2 little pins of the E-Brake hardware ( lost them ) and needs new E-Brake lever rubber boots. ( they ALL need new boots. )


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Old Aug 9, 2019 | 02:43 PM
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From: Belleville , Ontario , Canada
Car: 1984 Trans-am
Re: Drum to Disk Diff Swap

Hey thirgen brothers this weekend after putting a ton of work into my engine i,m upgrading the rear diff as well, My current diff is a stock 1984 drum open diff i don,t know what ratio but it a one wheel peel but in the winter i picked up a sweet 1990 posi diff with the aluminum calipers and the ratio is 3.42 from a 1990 formula firebird my black queen is a 1984 trans-am i seen some where in a post which i can not find about doing this i need to change the prop valve or something about a item from summit i can buy that does something so you don,t have to change the prop valve and if it comes down to having to change the prop valve can i just take a prop valve from a gm car that has disk brakes from a pick and pull or does it have to be from a trans-am/camero thanks for the help hope my post it not confusing
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Old Aug 9, 2019 | 08:44 PM
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From: Meriden, CT 06451
Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Drum to Disk Diff Swap

Here is the thread you want to start at: https://www.thirdgen.org/forums/brak...e-upgrade.html
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