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Brake options for 8 1/4

Discussion in 'Projects, mods, restoration' started by Dodgeboy49, Nov 12, 2017.

  1. Dodgeboy49

    Dodgeboy49 Active Member

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    I'm working on an axle swap in my 1949 Dodge 1/2 ton pickup. I've thoroughly worn out the stock rear end and have found it likely that I can switch to a newer axle more inexpensively than I can repair the many issues in the old one. I found a Chrysler 8 1/4 inch rear axle from a 1991 Jeep which is so near to a perfect fit as to be unbelievable. The ratio is just a bit higher than stock, which I'm hoping will bump my top speed from 55 to 60 mph. My biggest concern is that the stock Jeep brakes are 9" drums with (I think) 13/16" bore cylinders. The original brakes on the Dodge are 11" drums with 1 1/8" bore cylinders.

    I'm wondering if there are any options for installing 11 inch brakes, or perhaps larger bore cylinders to 9 inch drums? The rest of the braking system on the truck will remain unchanged, so I'm hoping to find something that will be reasonably close to the original in terms of braking power, or at least not reduce the effectiveness of the brakes.
     
  2. pt006

    pt006 Active Member

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    Matching drum diameters and wheel cylinder diameters with master cyl. diameters can get complex. And, pick-up trucks have a variable load on the rear axle. So, they are designed to stop well with a full rated load, but will usually lock up the rear brakes when the truck is empty. My old D100 had 10" drums on the back and discs on the front. It stopped well with 500 lbs. Not so well with 2,000 lbs. If you use a truck empty most of the time, then less rear braking force is good. If you run loaded a lot, then more rear braking force is needed.

    Volare' and Aspen wagons [and others] had 8 1/4" axles with 10" drums. They also came with 11" drums, but I've never seen any. Maybe taxi or trailer tow? ------------- Let us know the final results and how you got there.
     
  3. valiant67

    valiant67 Rich Corinthian Leather
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    11” drums were used on 8.25” axles in Diplomat and Gran Fury police cars among others.

    I also believe the11” setup from a 9.25” axle bolts onto the 8.25”.
     
  4. Dodgeboy49

    Dodgeboy49 Active Member

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    Thanks for the info! Now I have some direction for my search.
     

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