Brake Conversion

Transmissions and Rear Ends

  1. The_Red_Barron

    The_Red_Barron Active Member

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    Hello,

    I recently got the car ready for inspection, and spent well over an hour trying to change tires and check brake pads in the rear. This is because the drums were not correctly set up, and I was fighting the ridge that was created in the drum......

    I've played with the idea before, but this event makes me want to convert to disk brakes all around.

    I currently have a 7 1/4 rear end, the original to my knowledge. are there any conversions I could do to this rear end, or should I get a larger rear end? I think we have an 8 3/4 that needs work, but I would also need to get gears and maybe a different yoke. And at that point, I may as well replace the joint at the front of the shaft, since it clanks when I shift from drive to reverse.

    My goal is to just use the current rear end that I have, but with a different brake set up......

    Any ideas?
     
  2. BudW

    BudW Moderator Staff Member

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    I just now read this – but not exactly sure what you are asking for/about.

    For brakes – the 7¼” FMJ differentials only came with 10” drum brakes. A person can fit 11” drum brakes on it (Dodge pickups and vans are good sources for all but the drums (most pickups are 5x5.5” bolt pattern wheels) and parking cables). Parking cables for 11” drums are still being made.
    11” drum brakes do require 15” (or taller) wheels.

    The Jeep Cherokee disk brake conversion can also fit and might be a good option – but they also require 15” wheels (or taller).

    Your original brake drums can get a ridge worn into them at the lip. In many cases, they can be machined out when they machine them when replacing brake shoes. If the drums are “too thin”, then new brake drums are not too expensive (if planning on just performing a brake job).

    When a person replaces brake linings (disk or drum), protocol dictates machining the brake rotors/drums at same time for better braking performance. That said, most people who perform brake maintaince themselves, don’t get the rotors/drums machined – which causes those ridges (on drums and on brake rotors).


    The 7¼” differential might hold a contest for the weakest differential out there – but holds up OK for /6 and small blocks (with up to mild modifications). Any more than that, I recommend you start looking for a replacement and have it at least under the workbench in garage (or somewhere) so it will be ready when the existing differential blows up.

    FMJ’s only came with two different differentials: 7¼” and 8¼”.

    ’65-70 B-body 8¾” and 9¾” (Dana 60) differentials will fit with minimal modifications. Other differentials will fit with “more modifications”.

    If you already have an 8¾” – then take some measurements off it and post here and I can tell you if it will work or what’s needed to make it work.

    The measurements needed would be the perch center to perch center, the WMS (Wheel Mounting Surface - the area the wheel meets the axle shaft or brake drum) to WMS, and if perches are located on top or bottom of differential.
    Measurements don’t have to be exact – for I know that is hard to do, sometimes.

    The yokes are interchangeable from 1970ish to present, with a couple of exceptions. The older yokes (on the 1969ish and older differentials) can match existing U-joints – so if you have an older differential, that isn’t a big issue.
    The ‘69ish and older differentials used 10-spline yokes and ‘70ish & up used 29-spline yokes.


    Upgrades to your existing 7¼”?
    Not really, other than gear ratios (decent ratios are hard to find) and limited slip (which is also hard to find). The aftermarket just didn’t do much with this differential – even though it has been in production from early ‘60’s to late '90's.
    BudW
     
  3. Dr Lebaron

    Dr Lebaron Well-Known Member

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  4. BudW

    BudW Moderator Staff Member

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  5. Duke5A

    Duke5A Well-Known Member

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    I'm going to be selling my 8.75" housing in the Spring. 4.10 gear, SG, 489 case. Will bolt right into an F/J/M.
     
    BudW and 80mirada like this.