Hi gang,

I've had a continous problem with my rear drums getting warped, or out of round, after about 500 milles on them. I've replaced them 3x and it still comes back. It seems to be worse on the right side.
When i put a brand new drum on and spin it, i can hear it "touch" the pads on the right side in one spot. All the pads, springs, etc have been checked out.
The truck drives great for the first 500 miles, then it starts hopping again

What could be causing this problem if its not the drums/brake assembly?
thanks!

-Mark

 

Wheel bearings or axleshafts. Pull the rear wheels off and see if the axle flange can be moved up & down, even a tiny bit. Then put the truck in gear (chock the front tires, but DON'T TOUCH THE BRAKE PEDAL while the drums are off) and observe the axle flanges. They shouldn't appear to wobble in the slightest. If the axle flanges wobble, the axleshafts are bent & should be replaced before any other diagnosis. If it clunks up & down, the wheel bearings are eating into the shafts. Click my black Bronco below & look thru the 8.8" Axle album.

Then put the drums back with at least 3 lug nuts to hold them on (you might also need some washers) and check them for wobble, then repeat with the rims/tires.

Ideally, NOTHING should appear to move in silhouette, but the tires will probably have some slight irregularities. If you think it's too much, find a shop that will "road-force" check them, and then "match-balance" them. Expect to pay $40-100 for that procedure.

 

Thanks Steve!

I will do that and report back. Probably wont get to it until tomorrow tho.
I suspected it could be an axle also. Any idea on how much one or both would cost? Hopefully not that bad since ive already spent way too much trying to fix this already!

-Mark

 

I've pulled both wheels and drums off. I didnt notice any axle movement. I did pull up and down on both and didnt see anything. When the truck was in drive, there wasnt anything wobbling badly.
What i did notice was on the right rear side, the brake was grabbing in only one spot. For every wheel rotation it would go 3/4 the way around, then slightly bind the other 1/4. It does this with brand new drums on it, so i know its not out of round drums.

What do you think?

-Glade

 

When rear brakes are setup properly, there isn't a lot of clearance.

Still wondering about a bent axle shaft. Or maybe bent wheel studs that bias the drum on the axle shaft?

The drum is attached to the axle. The shoes stay put. It seems that the problem is with the rotating assembly, somewhere?

 

Where should i be looking for axle play with it rotating?

I looked inside to where the axle sleeve can be seen and didnt really see any movement. There was no in and out, up and down......nothing.

Next i went and observed the end of the whole assembly (round edges) and did see an ever so slight wobble. When i put a straight edge at the VERY top of the round plate, and ran it straight across, it would not rub constantly around. It would skip in a few spots telling me it wasnt EXACTLY round.

Now......im telling you, this is verrrrry small, but could that be the axle or just an out of round plate?

-Glade

 

Have you looked specifically at the center 'hub' of the wheel flange, which the drum centers on? Also, does the bolt circle rotate without oscillation - that is, each bolt clears the same spot as it rotates by?

Not sure how accurate the wheel hub itself has to be, but the bolt circle and drum mounting hub need to be perfectly centered with respect to the centerline of the axle shaft.

Do you see any indication that the drum is rubbing the backing plate? May be a good sign that something is way out of spec.

This is a tough problem - drums shouldn't be this hard!

Any chance the shoes are dragging too much, causing an overheating issue?

 

I'm pretty positive the rub from the shoes are warping the drum due to heat. If i put it in drive on flat ground and just crawl along, i can feel the brake hitting that one spot. It also bounces the rear end on stops and basically hops down the road during normal driving. Its starting to drive me insane!!

Ill pull the drums off again and look specifically at the middle, and bolts for any out of round movement.

It doesnt sound like anything in the brakes/pads/drum because its only grabbing in that ONE 1/4 of the rotation. It seems like something is warped for sure. It HAS to be the axle or something in the differential maybe?
Could anything be out of round/worn in the diff causing the axles to wobble slightly? Probably not, since its the right rear that seems to be causing me hell.

I looked on summit and new axles are $99 each. Thats just the shaft tho. What else would i need to replace both sides?

 

Just a WAG - are you sure the emergency brake mechanism is fully released?

When you had the shoes inspected, were the shoe tabs lightly greased where they contact the backing plate?

Any possibility that the backing plate is not square with the axle, causing a misalignment of the shoes with respect to the drum? Not sure how one would go about checking this.

Thinking about the potential for the shoes not fully releasing/returning for whatever reason, and something that may cause the shoes to be in an off-normal resting position.

I realize the above suggestions are a stretch, but again, drum brakes should not be this difficult.

 

WDE, your "wag" is actually what ive thought for months now! I'm glad you brought it up.

I've thought that it could be something simple like that for the longest time. What or why would only one side be doing it tho? Is there a simple way to disengage the e-brake cabling to eliminate that from everything? Maybe.........the cable is just binding on the right side and not the left? Something like that perhaps??? BUT......how do i fix it if it is?!? Ok, nevermind, lets just figure it out first!

Thanks for all your inputs! As you can imagine, this is a tough one to figure out, but i dont want to shell out big $$ for nothing that will fix it also

-Glade

 

UPDATE!

Well, after 3 more hours on jacks, and brake dust flying everywhere, i think i figured it out. The E-brake was definitely contributing, but i think its the springs or a worn cable. When i had up, i messed around with the e-brake cable and got the rub to stop on one side and almost go away on the other. Then i had a rubber mallet and banged the backside of the housing to get chunks of brake dust out. When i did that, the wheel spun "almost" completely free! I can get it to bind hard, or not at all by simply hitting the housing in different spots.

I think that tells me that its got to be something with a worn spring or cable.

I eliminated E-brake alltogether because its completely disconnected and it still rubs.

How hard is it to replace the springs and/or cables in the assembly? Do they make a kit or something?

Thanks for the inputs, this one was tough!

-Glade

 

There are drum spring kits readily available that contain the shoe retaining and return springs, basically, every spring inside the drum except for the e-brake cable spring.

The e-brake cable spring looks to be integral with the cable, and a new cable comes with a new spring.

There is a drum brake spring tool - looks like a science fiction set of pliers. I've done OK just using a pair of larger channel-locks that have good gripping teeth (not worn down).

The return springs are probably the most difficult to stretch and get in place, just takes a little patience.

One suggestion is to jack the rear axle off the ground, remove both drums, then do one side at a time. If you have any questions, just take a look at the other one.

Be sure that there is a small dab of high-temp grease on the shoe tab where it rubs against the backing plate. Enough to lubricate, but not to transfer onto the lining.

Might be a good opportunity to clean all the dust out. Be careful not to breathe the brake dust. Some wet it and flush it out using brake cleaner.

 

Thanks wde,

I'll look around for the kit. Hopefully its not the E-brake spring causing the bind up. I've got the whole cable disconnected now, so i dont think so.
Something inside has too much play allowing the shoes to move around. Thats what im betting on.

I will let you know how it turns out after i replace all the internals.

-Glade