Author Topic: Rear Drums Sticking Only Going Forward  (Read 4977 times)

Offline JohnnyPopper

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Re: Rear Drums Sticking Only Going Forward
« Reply #15 on: December 26, 2019, 12:59:05 PM »
Bruce can you remind us (well, some of us) what FF stands for? I know I'm going to feel dumb...  :o
1957 Apache 3100 235 Inline 6, 3 on the tree
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1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: Rear Drums Sticking Only Going Forward
« Reply #16 on: December 26, 2019, 03:04:45 PM »
Full Floater

The axle is simply a mechanical coupling to the wheel hub and supports no weight of the vehicle.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline JohnnyPopper

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Re: Rear Drums Sticking Only Going Forward
« Reply #17 on: December 26, 2019, 03:21:38 PM »
Thx VZ, I'm smarter now  ;D
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Jon87V20

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Re: Rear Drums Sticking Only Going Forward
« Reply #18 on: March 25, 2021, 11:12:13 PM »
Sorry for reviving such an old thread, but I’m not sure it was worth creating a new one.

I pulled the drums off and completely disassembled the driver side. It looks like the lands are pretty beat up. Is it okay to try and clean them up with sandpaper? I really don’t want to pull the axles and replace the back plates right now. I just spent $270 buying new drums, shoes and hardware and the back plates aren’t cheap.

1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline bd

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Re: Rear Drums Sticking Only Going Forward
« Reply #19 on: March 26, 2021, 10:52:09 AM »
It depends on how deeply the backing plate is grooved.  If the grooves are shallow, using a sanding disc on a right-angle die grinder should work.  Otherwise, the grooves can be filled by brazing and then trued flat with a sanding disc.  Be sure to lube the lands with a dab of grease during reassembly.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Jon87V20

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Re: Rear Drums Sticking Only Going Forward
« Reply #20 on: March 26, 2021, 11:56:05 AM »
Thanks, bd. There's a pretty bad ridge on one of the lower lands on the side that wasn't even sticking so the other side is probably worse. That's a bummer. If I take the axles out to change the backplates, that doesn't involve any of the tolerances etc. that a professional has to set up right? You can just slide the axles in and out once you remove the pin? I just paid thousands of dollars to have both the front and rear differentials redone and don't want to mess anything up.

I was also wondering, is there a certain type of grease I should be using for the drum brake hardware, or is normal bearing grease okay?

Thanks again. I appreciate the help.
« Last Edit: March 26, 2021, 12:46:05 PM by Jon87V20 »
1987 Chevrolet Suburban V20 Silverado
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Offline bd

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Re: Rear Drums Sticking Only Going Forward
« Reply #21 on: March 26, 2021, 12:20:39 PM »
Frankly, I would braze it up in place using a nickel silver brazing rod.  No need to disassemble past removing the shoes.  Viscous, white lithium grease is generally used to lube the lands and self-adjusters.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Jon87V20

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Re: Rear Drums Sticking Only Going Forward
« Reply #22 on: March 26, 2021, 12:47:16 PM »
I don't have any experience with brazing. Is that something anyone can do with a decent tutorial video or something?
1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline bd

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Re: Rear Drums Sticking Only Going Forward
« Reply #23 on: March 26, 2021, 02:03:37 PM »
If you can solder or weld using a flame, you can braze rather easily.  Otherwise, it's not a difficult skill to learn fairly quickly, but I recommend practicing on some scrap metal initially to get the hang of it so that you feel comfortable.  Practice with flux coated brass rod on scrap pieces then switch to flux coated nickel silver rod to repair the backing plates.  The biggest expense is in preparing if you don't have any of the equipment.  You will need welding goggles and gloves, a torch setup, and gas(es).
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Jon87V20

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Re: Rear Drums Sticking Only Going Forward
« Reply #24 on: May 15, 2021, 12:05:29 PM »
Just wanted to throw an update out on this. After finding most of the lands on the backplate were pretty beat up, I elected to just sand them a bit to take off any sharp or rough edges and put some fresh lithium grease on them. So far, things seem to be going well. However, I do still hear a bit of a squeak after several slow downs on the highway then rolling slowly in gridlock traffic.

I'm also still getting shuddering from the rear end under heavy braking. I'm wondering if maybe this has something to do with the combination valve (proportioning valve?). The reason I say that is, I've noticed when braking, I can feel a slight resistance in the first few inches of pedal travel where I can feel the truck actually begins braking, then further down with more travel, I hit harder resistance and there's significantly more braking force.

Could this be that the drums are that first grab I'm feeling happening way before the discs grab as well? I'm thinking the shuddering is maybe the drums are being way over-engaged by the time I have my foot hard into the pedal like that? To be clear, they are NOT locking up though.

By design, all four brakes in theory should be engaging at the same time correct? Isn't that the main function of that valve?

Hearing this, would anyone recommend looking at replacing the combo valve?

Thanks!
« Last Edit: May 15, 2021, 12:08:03 PM by Jon87V20 »
1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline VileZambonie

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Re: Rear Drums Sticking Only Going Forward
« Reply #25 on: May 17, 2021, 02:43:37 PM »
Sounds like you need to resurface the drums.
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Offline Jon87V20

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Re: Rear Drums Sticking Only Going Forward
« Reply #26 on: May 22, 2021, 11:57:03 AM »
I just put some brand new ones on. They claimed to have resurfaced the old ones too.
1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline VileZambonie

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Re: Rear Drums Sticking Only Going Forward
« Reply #27 on: May 22, 2021, 03:57:27 PM »
...and?
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Offline Jon87V20

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Re: Rear Drums Sticking Only Going Forward
« Reply #28 on: May 24, 2021, 04:42:19 PM »
I just meant that as a reply to what you said about resurfacing. Everything in there is new. Drums, shoes, and all the hardware. Still having some symptoms albeit not as bad as before.
1987 Chevrolet Suburban V20 Silverado
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Offline VileZambonie

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Re: Rear Drums Sticking Only Going Forward
« Reply #29 on: May 24, 2021, 05:14:07 PM »
So you replaced the drums and it's still the same? If everything is as you say, it sounds like it's your front brakes.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10