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Braking vibration

Rickb1b

Sr. Member
Joined
Feb 29, 2012
Messages
443
Anyone ever get a grabbing/pulsing caused by the drum brakes. I’m getting a brake pedal feel just like a warped rotor. Only problem is my rotors are bran new. Also I checked the disc runout and it’s at .002 or less. However my drums aren’t new, but never encountered this befor with the drums.

BTW, I called to check on getting the drums machined; they wanted $40 each. New ones only cost $35. No wonder all the machine shops are going out of business. Back in the day, NAPA would machine brake drums for next to nothing.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,344
Yep, it's a vicious circle now. Imported parts are WAY cheaper than the labor for a guy that wants to own a home too.

A couple of things it can be, in addition to the brakes, would be the tires (or just one tire) or wheel bearings.
Typically the wheel bearings don't just happen all at once, but if they were not properly torqued down the last time, one or both fronts could have come loose.

Believe it or not, a braking vibration can also be caused by the rear driveshaft. Not as common as an acceleration vibration, but it can still happen.

When did it start? Any servicing done right before? Tires are old? Driveshaft been serviced lately?
Even loose motor mounts can create an issue where a tiny bit of the engine might be touching something metal and causing the vibration through the body.

Do you feel it in general, or only through the brake pedal?
If only through the pedal, then it's either the brake shoes/drums anyway, or the bearings, or the tires.
At least those are the only things I can think of at the moment.

Good luck.

Paul
 
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Rickb1b

Sr. Member
Joined
Feb 29, 2012
Messages
443
Not much past data to draw on with this bronco. It was a complete frame off restoration and I’m in the final stages. Only have about 500 miles on it and as best I can recall it’s been there the whole time. I’ve been chasing down various vibrations since I got it in the road. Had a rear driveshaft vibration, so I got a complete new one. Had the transfer case touching the tub causing this low frequency hum, took I while to find that one. Fixed it with a little hammer clearancing. Rear end, axles and bearings are all new. So basically the only part of the truck witch isn’t new is the rear wheel drums. Also what led me to thinking drums; when I adjusted the brake shoes tighter, the vibration got worse. Meaning it started sooner when the brakes are applied.
 
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Rickb1b

Sr. Member
Joined
Feb 29, 2012
Messages
443
Ok Rusty, you may have hit on something. I thought the short shoe went on the front. I thought, as the front one grabbed, it forced the back one into the drum tighter. Thus, kind of self energizing. If indeed the short one goes in back, this could be my problem.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,344
You're correct. Primary (short) shoe is to the front, whether on the front or the rear brakes.

Paul
 
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Rickb1b

Sr. Member
Joined
Feb 29, 2012
Messages
443
Well just as a follow up. I replaced the rear drums and shoes, all is well now. This is a first for me, never had the drums cause a brake vibration.

Also, interesting, I was able to buy two new drums and shoes, delivered to Alaska for less the the shop wanted to machine my old drums. Go figure.
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,224
Loc.
Upper SoKA
Just now seeing this, and yes I've had that happen. Usual cause for me is to drive off with the p-brake lightly engaged on our CTD. That engine just doesn't care, can't feel it. Next thing I know, smoking hot rear brakes! Even though I do not use the p-brake while they're cooling they never cool perfectly round again, and will pulsate.
Fixing the brake light switch helped, but I still have to be careful that they fully release.
 
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