Dartman Posted May 8, 2021 Report Posted May 8, 2021 HI all I'm having trouble with my right rear brake locking up when I slam on the brakes aggressively. Here is what I've done and learned over the last 10 days - my own brake university 1950 1/2 ton in decent shape - rear seals and wheel cylinders leaking. Supposedly a brake job done a few thousand miles ago. Front brakes in good shape. I pulled the rear drums and axels. The drums looked good no wear lip and smooth. The shoes looked good but oil soaked. Seals leaking as well as wheel cylinders. Replaced seals, replaced wheel cylinders. Cleaned up everything and assembled and set major adjustment and minor adjustments to lowest point - zero adjustment. Noticed master cylinder leaking replaced that and bled and flushed brake system - all new and clean fluid throughout. Since assembly I've adjusted rear brakes using the minor adjustment to get drag on rear wheels. I also adjusted front brakes - again just to get a light drag on front wheels. I have a nice hard pedal and truck brakes evenly. Brakes work great under normal load. However, when I slam on brakes at 40 MPH truck stays straight and true and while I can feel all wheels braking my right rear will lock up. This sounds like the job was straight forward but over a 10 day period I have had this apart and back together at least 6 times. I've had the shoes arched to fit drums the shop didn't want to turn drums said they looked good and didn't want to risk taking off to much material. Any ideas ? FYI - Lessons learned 1. shoes come in std and oversize (couldn't get drums back on) - they gave me oversized at first and replaced with std later. 2. Wheel cylinders, Raybestos, came with pins (cylinder to shoe pin that pushes shoe out when brake is applied) 1/2 inch to long (creates the problem of adjustments not working) I had to use old pins from original cylinders. 3. it matters which holes are used for retraction springs - I had one spring in top hole and it was to mush tension and forces mating cylinder to activate before the other (one shoe making contact before other) . Instead of using a slide hammer to pull axels I made my own puller which works great - picture attached. OK with all of this does any one have any ideas why the right rear locks up when braking aggressively? I look forward to any and all ideas- thanks Steve Quote
JBNeal Posted May 9, 2021 Report Posted May 9, 2021 If right rear is locking up, left rear is probably not engaging fully. Brake spring should only be for brake shoe retracting, I think the different holes were for different applications where there might be wheel cylinder interference. As long as the spring is partially extended when installed while the shoes are pulled all the way in, the shoes will have the spring's resisting force to overcome when brake fluid pressure is applied to the wheel cylinders. The one piece spring should hook over each shoe, not sure why one spring end is hooked behind the shoe. Quote
Young Ed Posted May 9, 2021 Report Posted May 9, 2021 Did you replace the contaminated shoes? My 46 got a little fluid on the shoes and will lock up the wheel until I brake a few times. If yours was soaked you may never get them clean enough Quote
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