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1959 B46 Brake chamber size & differential

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I'm rebuilding '59 B46 and have some brake questions.

  1. Brake chamber sizes: I have Type 12 on the front (5-11/16" dia.) and Type 30 on the rear (8-1/8"). Is this a common configuration?
  2. The rear chambers are mounted on two different cast brackets - one cast iron, one cast alum. They are different shapes. I'd like to replace the right (alum) to match the left (iron). Or...
  3. There are chamber brackets welded to the differential. Looks like I'd need a lot of parts ($$$) to move the chambers to these bracket. 

And ... some additional photos.







Smaller PC011082.jpg




Edited by Keith S
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once you've painted the brackets who's to know.that is the right booster sizes because of the lining size and diameter.if you V out the crack on hub and weld it up it will be as good as new. it is done all the time.405th B46 made .not bad.the crd number is style the next long number is the part number and the last is the ratio. hope this helps you.

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  1. The chamber brackets: When I was taking Before pictures I noticed that when viewed from the front of the truck, the left chamber (mounted to the alum. bracket) is much closer to the ground and at a different angle. My first thought was - wtf. That's why I want to replace it. So far I haven't found anything close to either one. Any idea on who might have one?
  2. I might repair the wheel hub.
  3. As for the gear ratio... A quick check; The driveshaft turns 3+ times to once for the wheel. Could it be a 3.54? I thought I read that some of the stamped numbers dealt with tooth count? Maybe that wasn't for a Mack?
  4. As for the differential: It's a dual reduction and has a ton of backlash - the driveshaft has maybe 5 degrees of play. Is this normal if the differential has a Power Divider? I'm going to change the fluid so I'll get a quick look down the filler hole.


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looks like a mix match of parts. usually Mack used the brackets welded to the housing for the X trucks or dump trucks to keep the cans up high and out of the way for rocks. I have one of these housings layin around. they used the big offset slack adjusters and a bushing that was bolted to the bolted on can bracket holes in your picture.


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  • That aluminum chamber bracket was a mess - some serious galvanic action. Someone did a little grinding on the S-cam shaft to align with the slack adjuster.
  • I found a pair of chamber brackets and slack adjusters for a CRD78. Naturally these were in the NE. How is it that everything is located in the NE?
  • Brakes are a little worse than I thought. Left side is dry.

Questions: I'm looking for:

  1. Brake shoe linings
  2. Wheel bearing seals
  3. Hopefully not drum(s) but...
  4. Maybe an S-cam shaft
  5. S-cam bushing kit(s)
  • Are these things off-the-shelf items?
  • Should the clevis pin and slack adjuster be a snug fit?
  • I used serious heat to remove the clevis pins. Are these usually replaced after heating?
  • Is there a spring kit for the brakes?
  • Big socket for adjusting the bearings - how expensive is this?

Advice and ideas on what else to look for.



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