14 bolt, Full-floater drum brake squeak?

[Daveo91Burb]

I've got what I think is just a drum brake squeak on my left rear. One squeak per wheel revolution and it goes away with a light tap on the brake pedal. Was intermittent but it's now pretty much constant at low speeds (can't hear it at higher speeds but may still be there). The noise isn't real loud and it wouldn't bother me if knew it wasn't causing any problems or damage. I've replaced the shoes and all the springs and stuff in there in the last year - shouldn't be down to the wear indicator yet. I would have taken a look in there before posting if it wasn't such a PITA to get the drums off a FF. Hoping someone will have some insight and let me know if I have a problem or not.

The guy before me traded out stocker axles for those from a '77-ish 3/4 ton burb with 4.10 gears and FF 14-bolt.


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[Daveo91Burb]

Bump. Any thoughts on this? Need to decide if I need to pull the drum to take a look. Thanks!


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[Georgeb]

Sounds like a slightly out of round drum. Your shoe is rubbing on the low spot in a static state. You can try adjusting it up a little or you may need to turn the drum.

 

[Daveo91Burb]

Thanks! That's what I was thinking too - I'll try adjusting. When I rebuilt the rear brakes I took the drums to a parts house to have them turned. They wouldn't do it - just slightly out of spec. I elected not to replace them I might be living with that now


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[chengny]

Thanks! That's what I was thinking too - I'll try adjusting. When I rebuilt the rear brakes I took the drums to a parts house to have them turned. They wouldn't do it - just slightly out of spec. I elected not to replace them I might be living with that now


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Look closely at the condition of the backing plate and especially the contact pads. Although there is not any relative rotary motion between the brake shoes and the backing plate, there is a certain degree of linear motion that occurs - when the wheel cylinders force the shoes out against the drums. Even though the shoes are held tightly against the backing plates (by the mounting/hold down springs), the brakes are engaged by hydraulic pressure so they rarely (if ever) stick on the way out.

But when the brakes are released, the only force that returns them to the free wheel position is what is provided by the return springs. For that reason, the inboard edges of the shoes must be able to move freely across the 6 contact pads. If the pads are trashed they tend to prevent the shoes from fully releasing. The linings will then stay in contact with the drums causing premature wear. Or, as noted below, if the pads are modified - in an attempt to restore the smooth surface - this results in misalignment and grabby/noisy brakes:

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Nickel Never-seize seems to work best as a lubricant - and it stays put between brake jobs:

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BACKING-PLATE INSPECTION

Contact Pads - Clean the contact pads thoroughly and verify they are not burred or grooved. Burrs may be removed with very light sanding. If the contact pads are grooved the backing-plate should be replaced.

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NOTE: Grooved contact pads may cause the rear brakes to drag or stick. If you attempt to remove the grooves by grinding or filing, the new shoes/linings will not line up correctly with the drum. This may result in the problems noted above.

The contact pads should be coated with a high temperature silicone lubricant prior to reinstalling the shoes/linings.

Mounting Bolts - Verify the mounting bolts are secure. A loose backing-plate will cause the rear brakes to be very sensitive or grabby.


But then again - after having said all that - maybe its something simple. Like your e-brake cable is not releasing completley.

 

[chengny]

I would have taken a look in there before posting if it wasn't such a PITA to get the drums off a FF.

If you just want to inspect/repair your brakes, I wouldn't stress about pulling the drums for access. It isn't a big job - maybe 2 or 3 hours. Some dwgs and the procedure below.

The 10.5 14B FF used in the mid 80's:

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The earlier version is disassembled in a similar fashion:

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1. Remove wheel and axle shaft.

2. Disengage tang of locknut from slot or flat of locknut, then remove locknut from housing tube, using appropriate tool, Fig. 6.

3. Disengage tang of locknut from slot or flat of adjusting nut and remove locknut from housing tube.

4. Use appropriate tool, Fig. 6, to remove adjusting nut from housing tube.

5. Remove thrust washer from housing tube.

Pull hub and drum straight off axle housing. Done. The bearings will come off along with the hub/drum assembly - and stay in place:

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[Daveo91Burb]

Thanks for all the info! Really appreciate it. On Friday I took the burb on a 200 Mile trip and in anticipation of that, just to be sure, I did ended up pulling the drum to check things out. You're right - it didn't take as long as I remember, probably because I more or less knew what I was doing this time. I didn't see any of the issues you mention, no grooving in anything. Although I didn't really take a close look at the contact pads... I'm hopeful I would have noticed if there were problems. I put it all back together and the squeak is still there (occasionally), but I'm thinking you might be on to something with the e-brake. This is a 91 but axles are from a 77 so the cables are completely different. The PO didn't have the e-brake hooked up at all but I've spent a lot of time trying to engineer a connection between the two different systems. I still don't have it quite right - I really only can get engagement on the drivers side (where the squeak is). Today I took it on a short drive; when it squeaked I just engaged the e-brake one or two clicks for a few seconds while driving and it stopped the squeak for the rest of the trip.


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[Daveo91Burb]

Sorry to revive an old thread, but it's mine so hopefully that's kosher. I finally sprung for new drums to hopefully solve the squeaky brake problem - no luck. When replacing, I addressed the issues @chengny describes in the quote. I felt I didn't need to replace the shoes and all hardware since they're like new. I also didn't pull the shoes all the way off, but I undid the hold-down pins so I could pull the shoes away to inspect the contact pads on the backing plate. I cleaned, lightly sanded, and greased with CRC brake grease, per the advice. There was some light grooving, but it wasn't as bad as in the pics below. Put everything back together and actually took it on an 80 mile drive today - still squeaking, possibly even worse than before.

I guess my next step is to replace the backing plates per the advice? Those seem to be kind of hard to find. Couldn't find them on RockAuto or Autozone. Might be able to find them on Amazon with enough searching. Judging from prices I've seen I'm probably looking at another $100 at least. Man, with the drums I just bought and the price of new backing plates, that would have got me a lot closer to a rear disc conversion. If there was a low buck conversion that included parking brake I probably would have done that already. Damn.

Other (less $) things I should try first?

New shoes? (maybe they're damaged and I'm not seeing?)
Could it be the wheel bearings?
Have my brand new (Autozone) drums turned?
Adjust brakes looser? Or tighter? I adjusted until wheel all but locked up, then backed off 6-8 clicks or so.

Look closely at the condition of the backing plate and especially the contact pads. Although there is not any relative rotary motion between the brake shoes and the backing plate, there is a certain degree of linear motion that occurs - when the wheel cylinders force the shoes out against the drums. Even though the shoes are held tightly against the backing plates (by the mounting/hold down springs), the brakes are engaged by hydraulic pressure so they rarely (if ever) stick on the way out.

But when the brakes are released, the only force that returns them to the free wheel position is what is provided by the return springs. For that reason, the inboard edges of the shoes must be able to move freely across the 6 contact pads. If the pads are trashed they tend to prevent the shoes from fully releasing. The linings will then stay in contact with the drums causing premature wear. Or, as noted below, if the pads are modified - in an attempt to restore the smooth surface - this results in misalignment and grabby/noisy brakes:

You must be registered for see images attach

Nickel Never-seize seems to work best as a lubricant - and it stays put between brake jobs:

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

BACKING-PLATE INSPECTION

Contact Pads - Clean the contact pads thoroughly and verify they are not burred or grooved. Burrs may be removed with very light sanding. If the contact pads are grooved the backing-plate should be replaced.

You must be registered for see images attach

NOTE: Grooved contact pads may cause the rear brakes to drag or stick. If you attempt to remove the grooves by grinding or filing, the new shoes/linings will not line up correctly with the drum. This may result in the problems noted above.

The contact pads should be coated with a high temperature silicone lubricant prior to reinstalling the shoes/linings.

Mounting Bolts - Verify the mounting bolts are secure. A loose backing-plate will cause the rear brakes to be very sensitive or grabby.


But then again - after having said all that - maybe its something simple. Like your e-brake cable is not releasing completley.

 

[75gmck25]

Years ago when I had my brakes done by a local shop, the owner complained that it tool him several sets of parts to get all the right pieces for my brakes. He said that it was hard to find all the right parts that matched the original.

The only trouble I've had since then is that the shoes are very grabby if the truck sits for a while in humid weather. The first few times I step on the brakes I get complete lockup (which impresses neighbors who might be watching), and then it settles down and works normally after the moisture burns off.

My e-brake mechanism was broken and the cable was missing when I got the truck. I bought a new cable from lmctruck, and then fabricated my own retainers that are similar to the original. The cable is just a big U-shape, with the cable from the pedal mechanism holding out one corner of the U and a bent piece of 1/2" rod holding out the other corner. The open pieces of the U are connected to each brake. The cable from the pedal has the adjuster you use to tighten the cable.

Bruce

 

[Blue Ox]

So this happens when the brakes aren't applied?

There's no wear indicator on shoes. Are you sure everything is assembled correctly? Shoes facing the right way, springs in the right places? Are the wheel cylinders retracting fully? As far as the adjustment, I usually do it by play and not by number of clicks. I set them for about 1/16" play, but either way it's not abnormal for the shoe to rub slightly and it shouldn't make noise.

 

[Blue Ox]

The only trouble I've had since then is that the shoes are very grabby if the truck sits for a while in humid weather. The first few times I step on the brakes I get complete lockup (which impresses neighbors who might be watching), and then it settles down and works normally after the moisture burns off.

Mine has done that since it was new. It's probably happening to you now that the brakes were put together correctly. I say it's rust, caused by moisture, not the moisture itself.

 

[Daveo91Burb]

Years ago when I had my brakes done by a local shop, the owner complained that it tool him several sets of parts to get all the right pieces for my brakes. He said that it was hard to find all the right parts that matched the original.

The only trouble I've had since then is that the shoes are very grabby if the truck sits for a while in humid weather. The first few times I step on the brakes I get complete lockup (which impresses neighbors who might be watching), and then it settles down and works normally after the moisture burns off.

My e-brake mechanism was broken and the cable was missing when I got the truck. I bought a new cable from lmctruck, and then fabricated my own retainers that are similar to the original. The cable is just a big U-shape, with the cable from the pedal mechanism holding out one corner of the U and a bent piece of 1/2" rod holding out the other corner. The open pieces of the U are connected to each brake. The cable from the pedal has the adjuster you use to tighten the cable.

Bruce

Thanks. I'm going to try and loosen the e-brake completely just to make sure it's not the culprit. I've had e-brake problems since day one. I actually bought it with no e-brake - PO put in a 14 bolt FF from a '78, but in the early 80s they changed the e-brake cable system drastically. The old system has an equalizer system with cables running along both frame rails, but the later system has just a single cable from the pedal down the DS frame rail, and then has a splitter going to the PS wheel. The two systems are not real compatible. I've thought about converting to the old system, but I'm probably missing holes and attachments for the cable guides. I've done some engineering to make it work somewhat, but it's still not quite right.

So this happens when the brakes aren't applied?

There's no wear indicator on shoes. Are you sure everything is assembled correctly? Shoes facing the right way, springs in the right places? Are the wheel cylinders retracting fully? As far as the adjustment, I usually do it by play and not by number of clicks. I set them for about 1/16" play, but either way it's not abnormal for the shoe to rub slightly and it shouldn't make noise.

I'm pretty sure everything is assembled correctly. I know the front and back shoes are different and I remember taking pains to make sure I got it right. But it's been a while. I'm ordering some new Delco shoes in case there's damage to the existing ones in there. Fairly cheap thing to try. I'm not seeing any new backing plates for the 14bolt FF anywhere.