Thank you very much for being clear concise and having an overall excellent visual. This is exactly the way I needed this presented to understand it. I especially like the tip about the 180° turn meaning the brake drum is out of round. This has helped me immensely.
Great video. Would the differential have to be disconnected from the drive shaft for the rotation test? In neutral the wheels would face a little drag from the transmission right?
Well, if it has a positraction or limited-slip differential then there would be some drag. But If your vehicle doesn’t have either of those, then each wheel will spin freely. You can only adjust one wheel at a time anyway. :-) With the rears jacked up, if spinning a wheel and the other spins In the opposite direction, then it doesn’t have any sort of positraction.
hi xmech, i figured out why my truck have a death wobble. the culprit was the drum brake wheel cylinder leak oil on the driver side. i replaced brand new wheel cylinder, shoes, star adjuster and the drum on both side but after i replaced i drove for 3000 miles and now the shoes pad dragged and locked on the driver side drum( i dont know if it is the star adjuster cause all the brake dragging or the bellcrank because i could tell when i pull on the hand brake and it get harder)i want to know what is your opinion. i forgot to mention to you after i did the rear brake i bleed all the brake except the sensitive proportion brake valve, do you think that can cause the shoes pad dragged on to the drum(only the driver side)? i putted 3000 miles after the rear brake replacement, should i just bleed only the sensitive proportion brake valve or should i start all over and bleed the whole brake system? thank you.
I remember you. Your problems started after you had the driveline and rear brakes changed. You need to clarify something, in this latest write up you said ...wheel cylinder leak *oil* on the driver side. Wheel cylinders don’t leak oil, they leak break fluid. This is a very important distinction! Though both differential oil and brake fluid will cause drums to lock up. Vehicles that leak differential oil have a smell about them, especially in the rear. Vehicles that leak brake fluid don’t have a smell. ---> If it was *oil* you botched the job, you didn’t fix anything by changing the drums, friction material, and adjusters. You absolutely have to pull your axle and replace the seal, using brake clean, clean all residue of oil from your friction material and related brake parts. if the leak was bad enough you might need to replace the friction material again. ---> If you miss-spoke calling brake fluid oil i.e. it really was brake fluid leaking, then you may have only have a adjustment problem. Only in extreme circumstances would air in a brake system cause one side to lock up, and would manifest it’s self in a soft pedal, which you don’t mention. And no, the proportioning valve is automatically bleed when a system is bleed correctly, put it out of your mind. Bleeding brake correctly: I have a bleeding video on my site to help you with this, most hobby guys don’t get a 100% of the air out. it’s called *Bleed brakes and no need to bench bleed master cylinder* watch it! And don’t freak out about using water, as some do, it’s perfectly fine to use water, warm beer, brake fluid, piss, or whatever... i tell people to use water so the can easier see when the bubbles and all the old fluid are gone. There is a part 1 and part 2 to the video. Because this is probably your first time using this system, have another person watching for the bubbles to go away, and only clean fluid to appear. bleed all four wheels using this system! You posted this write up on the appropriate video, so if you followed this video i don’t think you botched the adjustment job, which could cause your wheels to lock up, but it is possible your adjustment is wrong. ---> Pulling the rear drums again could tell you a lot, if either side is oil soaked replace the seal and clean all parts. looking through the brake adjuster holes in another way to check for oil. look on youtube for how to replace a axle seal on your particular year vehicle, i’m sure ones there. If everything is cool back there, use my fluid check valve system and bleed your entire system again, making sure the you adjust the drums like I suggest in this video. My instincts here are, it was *oil* and you still have a problem. let me know what you find out.
thanks for your the quick response, yes i did make a wrong term for oil, its was brake fluid from the wheel cylinder on the driver rear brake and i replaced both side with brand new wheel cylinder, drums,brake shoes, brake kits part and only the driver brake adjuster (because the driver wheel cylinder leak damaged when i took it off). the truck drive perfectly after 3000 miles the driver side rear brake started to drag and lock up (the driver rear brake only). by the way there isnt any rear differential oil leak in the brake and it was dry. do you think the brake adjuster, shoes pad or the drum are the culprit? the burning smell was come from the driver rear brake locked up while i was driving from my friend places back to my house( like 30 miles, do you think i can damage my rear differential while driving 30 miles with one brake locked up?). i have heard the proportion valve can lock up the rear brake when it damage. i took the drum off for the third times to inspect the problem but cant find anythings going wrong with it. but today i used the truck and i can tell is starting dragging on it(because i felt it on the hand brake each time i parked the truck, the click on the hand brake was 9 after i put everythings back on and now is started to have 7 clicks). thank you so much for helping me out. ps. after the bleeding the all the brake, the brake pedal does not getting soft at all.
Ok, now that we’re on the same path, here’s the deal: There is something else i need to clarify, you keep using the words “lock up” as in “do you think i can damage my differential driving 30 miles with one brake locked up.” There is a big difference between a tight drum and one that is lock up drum. If your drum was *completely lock up* you would be dragging the tire, the friction would be applied to the tire rubber and not the brake drum (the drum isn’t moving.) A vehicle with a completely lock up drum isn’t drivable, you would catch the tire on fire, and that fire would burn your truck to the ground! What comes next assumes you have a tight drum and not one that is completely locked up. Your vehicle has a load sensing proportioning valve, what this means is, one brake line (the in side) of the proportioning valve splits into two different brake lines (the out side) of the proportioning valve, one going to each rear wheel cylinder. This does at least bring in the possibility of rear wheel cylinders getting different pressure fluid delivered to them. Say the piston inside the proportioning valve being stuck. A simply way to troubleshoot this is, brake open the bleeder valve when the drum is tight. if the proportioning valve is causing the problem then it will be obvious, because fluid will shoot out under pressure. After driving for a while and you detect the problem, get home jack up the rears and see if your driver side tire spins, if it doesn’t open the brake bleeder, if brake fluid under pressure shoots out, then it’s hydraulic related (could be the proportioning valve.) if fluid doesn’t shoot out it’s mechanical related, i.e. tight adjustable, or a out of round drum, etc. Your job is to see if you can determine if it’s hydraulic or mechanical. P.S. if you are driving with a completely lock up drum, make sure your insurance is paid to date!
I thought of something else, in both of these write ups you bring up the parking brake. If the left side rear brakes had a parking brake cable independent of the right side parking brake cable, and those cables actually go through a outside housing, then there is the possibility the left side cable is not completely releasing. In other words, your driving around with the left side parking brake slightly applied. But if the parking brake cables directly attached to your rear brakes backing plates don’t have an outside housing, then this scenario is way less possible. There’s isn’t much of a chance for the cable to get jammed up. That said, make sure your parking brakes fully release! Jack up the rear, apply the parking brake 20 times, each time you release the parking break spin the left wheel and see if the parking brake fully releases each time. 7-9 clicks on a parking brake with correctly adjusted rear brakes, at minimum, indicates some stretching going on in your parking brake cables. Which is the exact opposite of a tight cable. A tight parking brake cable is what you would look for if it was responsible for a tight drum. A tight parking brake cable would equal a tight drum, but the brake fluid at that bleeder wouldn’t be under pressure. A mechanical problem.
thanks so much for those value info, now i do know what is a lock up and dragging( the reason i thought is locked up because i can smell the burn and the hot surface of the driver rear side of the wheel), but my question for you is dragging like that can it cause damage to the rear differential or the wheel bearing? can a wheel bearing cause dragging or lock up? today i jack the truck up again and spin the both rear wheels then i found out the passenger rear side dragged and the driver side freely, what i founded out is the e-clip on adjuster on the driver side kind of loose, so i replaced with the a new one. hope that e-clip is the culprit but not sure if it is. ps. you mean i should open the brake bleeder if the drum getting tight not the proportion valve correct( the proportion valve also have the bleeder valve)?
