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Technical Old Mopar parking brake replacement

Discussion in 'The Hokey Ass Message Board' started by KenC, Jul 4, 2021.

  1. KenC
    Joined: Sep 14, 2006
    Posts: 644

    KenC
    Member

    I'm putting an A833 OD in my 56 Dodge pickup. Doing that removes the original trans mounted parking brake.
    I don't need a ratio change as my 4.10 with the A833 is almost perfect. So a complete rear end swap isn't needed. But I do need a parking brake. My original plan was to add a disk type brake to the Pinion yoke and I have one to use. Not really sure of its holding capacity though. Seems like a lot of leverage would need to be designed into the actuating system. So, it seems like adapting a replacement rear brake system complete from the backing plate out may be better. I'd have to select parts that fit the original drum diameter and the plate would have to place the shoes in the center of the drum.



    Maybe a trip to a salvage is in order. No hurry, as I'm working on fender rust right now and that will be followed by frame clean/paint and installing my 230 and trans.



    Anyone attempt this before????
     
  2. BJR
    Joined: Mar 11, 2005
    Posts: 7,143

    BJR
    Member

    I'd use the pinion brake since you already have it. It should hold fine with a 4.10 rear gear as the ratio is in your favor for holding the car with the brake.
     
  3. 51504bat
    Joined: May 22, 2010
    Posts: 3,015

    51504bat
    ALLIANCE MEMBER

    I don't know anything about Mopar A833 O/D trans' but Dodge did use trans mounted drum ebrakes on motor homes back when. Might be able to adapt something to your trans. But the pinon ebrake sounds much easier and my guess is that it will hold just fine. But that is just a guess. I'm sure others with more direct experiences will chime in.
     
  4. 325w
    Joined: Feb 18, 2008
    Posts: 5,647

    325w
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    You may find it difficult to find common E brake parts to go into the drums pinion brake might be best
     

  5. Budget36
    Joined: Nov 29, 2014
    Posts: 7,219

    Budget36
    Member

    Might also be a good time to change the rearend out? I’d assume that’s what would be needed or different backing plates/brake assy and drums to match to work with your rear. Obviously cables and such as well.
     
  6. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,700

    RodStRace
    Member

    In my experience, back of trans parking brakes all have a ball and trunion joint, which is not optimal compared to a slip yoke and U-joint.
    The pinion mounted aftermarket stuff is mostly for Fords, which have caliper mounting brackets designed for them and a way to attach the disc to the pinion. Don't know of any that would work on an old Mopar axle assembly.
    You can look into mounting more modern drum brake assembles with self-energizing, self-adjusting and E brake features built in and swap them on the end of the housing. Parts will be easier after, too.
    I don't have a magic swap chart to tell you which will bolt on, but I'd guess you will want to measure the backing plate mounting surface, bolt pattern, and distance from that flange to the surface of the axle end. Since the tapered axles and separate flanges went away in 1965, the early stuff might swap easier, but the later stuff might be better for the features mentioned.

    With a 4:10 ratio, you have a 4 to 1 advantage in stopping/holding compared to the same force out at the ends.
     
    Last edited: Jul 4, 2021
  7. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,548

    gene-koning
    Member

    There are reasons most guys just swap out the rear axles when they do this stuff.

    As stated above, the modern pinion e brakes are mostly designed for Ford rear axle assemblies. The caliper units bolt onto the rear axle assembly in places you will have no bolts, bolt holes, or places to add bolt holes. The rotor bolts to the pinion yoke, which probably isn't going to match up to your rear U joint yoke. To make them work, you will have to reengineer all the mounting brackets, not impossible if you have fab skills, but not easy either. There are guys that have done this before, and there was at one time an e brake pinion disc brake kits available for a Mopar rear axle (don't know if one of those kits are still available, or if they would even match up with your axle, they were offered during the performance era).

    The next option would be to adapt the less modern in the rear drum e brakes. If your lucky, your current rear brakes are either 10" diameter, or 11" diameter. Other sizes would probably be more difficult to locate backing plates set up for e brakes.
    Just finding matching diameter backing plates is just the beginning, you also need to find the backing plates with the correct offset from the axle flange so the "new" brake shoes fit inside the drums without dragging on the drum depth. The next concern is the E-brake stuff, once installed inside of the drums, it all needs to clear the tapered hubs and axles.

    From there, you will need to come up with the e brake cables that connect to the backing plates (probably the easiest part) but then you also need an intermittent cable that can connect both backing plate cables together that are the correct length so you can adapt your original e brake cable can pull on the intermittent cable to apply the e brake.

    The cost of adding an efficient e brake set up to your existing axle assembly will probably cost more (and be less effective) then upgrading to a modern rear axle and rebuilding all of its brake stuff. Gene
     
  8. jaracer
    Joined: Oct 4, 2008
    Posts: 1,220

    jaracer
    Member

    Your original parking brake was pretty marginal. A pinion mounted parking brake would probably work as well.

    One problem with a a driveline brake and an open differential is: if one of your rear wheels is on a surface with poor traction, the differential can allow it to turn in one direction while the vehicle rolls away in the opposite direction.
     
  9. goldmountain
    Joined: Jun 12, 2016
    Posts: 3,098

    goldmountain

    It would be a whole lot easier to swap out the whole thing.
     
    gimpyshotrods likes this.
  10. Flat Six Fix
    Joined: Feb 6, 2010
    Posts: 1,271

    Flat Six Fix
    Member

    Okay first of all, tailshaft parking brake on Mopar transmissions, are not ball and trunnion types.
    1946 on in Canada used cross type ujoint drive shafts on Chrysler Desoto Dodge and Plymouth.
    As well as Dodge and Fargo pickups, for the most part.
    I still have 2 such drive shafts in my stash.
    On your disc on pinion ebrake, might work fine.
    But as an Emergency Brake not likely.
    Single or double MC?
    Or just swap in a Mopar 8 1/4 diff, ebrakes part of setup.
    Cherokee axle, in 3.73 would be great..
     
  11. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,670

    gimpyshotrods
    ALLIANCE MEMBER

    Ford 8.8 rear axle, sourced from a vehicle that has the axle width of your choice, with a 4.10:1 OEM ratio, and a limited slip differential. The last one I bought was $125 at the yard. I used to think that the smaller 6-cylinder equipped trucks had the 4:10 gears, but I have now seen complete chaos of 7.5 and 8.8 rears, with all ratios, with every engine, so make sure you know what you are looking at.

    Or a Chrysler 8.25 from a Jeep Cherokee (as has been mentioned), or Dana 35C, or the rare "up-country" package Dana 44 from the same. In each case, the 4-cylinder equipped versions had 4:10:1 gears.

    You are far better off just getting a whole axle.
     
  12. Is your current rear end a 8 3/4 which Mopar had at that time ? Find a 56 to 64 car rear end and swap the backing plates over - you can figure out the cables and hand mechanism you want to use.
     
  13. KenC
    Joined: Sep 14, 2006
    Posts: 644

    KenC
    Member

    Tks. , I didn’t know 4.10s were commonly available in that axle. Looks like I’ll be swapping.
     
    Flat Six Fix likes this.
  14. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,670

    gimpyshotrods
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    They are out there.

    Just in case you don't already know this: Http://www.car-part.com

    You would select Axle Assy Rear (w. Housing)

    If you select distance and your zip code, that will show you a list of options to choose from Don't rule out axles set up for ABS. You just don't hook up the sensor. On my 8.8 it is driving my speedometer!

    Also, in the case of the 8.8, depending on the donor (and for reasons that only Ford understands) there are 9 and 10-inch drums, and later discs. There may be more than that. I am never surprised by Ford.
     
    Last edited: Jul 6, 2021
  15. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,700

    RodStRace
    Member

    To pile on to gimpy's post, if you do swap to any axle, but especially a Ford, get at least the YMM info.
    They loved to change things even mid-year. My brother had a 68 Ford that had all 67 under pinnings, which wouldn't be strange, but it was a supposedly model change year. 68 stuff wouldn't work. The wiki for them says they are the same gen.
     
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  16. Flat Six Fix
    Joined: Feb 6, 2010
    Posts: 1,271

    Flat Six Fix
    Member

     
  17. My 1956 Plymouth with 277 poly and 3sp overdrive has a 4 11 gears in the 8 3/4 hosing - non posi but I have that covered. You can find those gears in a lot of late 50's early 60's farm trucks as well.
     

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