When I bought my '07 NNBS 1500 I had shake whenever getting on the brakes. Being that I always do my own vehicle repair, I figured it wasn't a big deal at all. I would just put new rotors or drums on and everything would be fine.
I was lazy for a few months, and then moved from Indiana to Texas. After the move I took the time to replace just the rear drums. Nothing else. When I bought the truck the dealer had paperwork showing they had replaced the rear brakes. The pads looked fine, so I left them.
The brakes were good. For about a week. Slowly, the shake has been coming back. I'm pretty sure it's in the rear again, as when i get on the brakes I can see the tailgate/bed bouncing. (also I don't feel the shake in the steering wheel like I would with front brake issues.)
There must be something else going on, but I don't want to just start throwing parts at it. I need some ideas. I bought the drums from autozone, and have a warranty on them. Should I have bought some from a better store? Better quality drums? Should the shoes, cylinders, springs, backing plate, etc be replaced?
I will try the parking brake thing today to see if it pulses. I think it will since when I'm barely on the pedal, I can feel the shake.
I always use Delco drums and rotors. Just put a set on mine a few months ago and all is well. There is a little pulse in the back, but nothing that I would say is "abnormal".
It has always felt like this truck brakes with the rear more than the front. I've never understood that as there should be preset bias front and rear. Also when I replaced the drums, when I took the tires off I could just pull the drums right off. (Like the brake shoes weren't touching the drum at all at rest.)
Typically drums warp from excess heat. Have you been pulling heavy loads and making hard stops?
Also make sure the parking brake is working propertly. If its dragging on the rear brakes they will run hot and one drive thru a water puddle with hot drums could cause warping.
Actually, you should hear a faint touching when you spin the drum on the hub (foot not on the brakes). Not dragging, but a tiny touch.
This applies more to 4 wheel drums, but still a good rule to follow so you know you have them set evenly.
Since replacing the drums, I have not towed anything. I live in Dallas now so there is alot of stop and go traffic, but I haven't had to make any emergency stops...
I don't think I've done anything to cause this. (Also I just read about "setting" the pads. I didn't do that. (I've never done that.)
I don't use my parking brake but will check and make sure it's not dragging. I think when I did the rotors the last time that both sides spinned freely.
Is there a reason to think that it would be braking harder with the rear? Is there an adjustable valve anywhere?
replaced both rear drums on my 05 sliverado new out of the box ac delco and had to take them and get them both turned they were bad right out of the box warped toward the outer edge now its nice and smooth
Pull the drums and make sure the shoes are properly installed. If installed properly, make sure the points where the shoes hit the backing plate are lubed. Also make sure the backing plates are not warped or otherwise damaged. A damaged or non lubed (at lube points) backing plate can cause shoes to hang up when applied, and then when you back up, they will release and may not hang up again for a while. And Murphy says when you pull go to pull the drum off, they will not be hung up at that time. (A dial indicator can be used to check the backing plate to see if it is bent.)
If backing plates look ok, put some high temp brake grease on the lube points (normally about six) and re-install everything. (And make sure the drums are round.)
So, here's something interesting that I've never encountered before.
In the morning, during the drive to work or wherever, the brakes are perfectly smooth. (at first)...
It seemed, (I really paid attention this morning) that when I left the house the brakes were smooth. During the drive, I slowly started to notice some grabbing in the rear brakes. (I still think it feels like the rear brakes, but could be wrong) It's almost like as the brakes get warm, they start grabbing.
Is it possible that there is an irregular section in the drums? One that heats up, or expands more than the rest of the drum? If they are smooth when cold, then it seems that one area of the drum is expanding more than the rest.
New drums typically need turning when you take them out of the box. I've never seen a brand new drum perfectly true. With that being said,
What kind of shoe are you using?
Organic, metallic, ceramic?
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