Jumpy Brake Pedal

[bwood]

I'm having trouble with the brakes on my 98 1/2 ton Sierra. The pedal pulsates violently and the truck shakes. I went to the front brakes and the discs were warped out of the range of being turned, so I figured this has to be it, I replaced the discs, pads, and bearings. Problem still existed. I went to the back brakes drums were out-of-round and covered in burned spots. I took them to be turned and the shop said they have already been turned, so once again, I replaced the drums and shoes. Seemed to fix the problem. The parts were on for about 2,000 mi and I took a trip to Austin and the pulsating began again, but not as severe. Now at 6,000 mi the problem is back in full force. I took the new discs to be turned. They were barely out. Put everything back together, didn't get any better. I am going to pull the drums this weekend. I fear that they are going to look like they did the first time. Has anyone had the same or similar problems with their truck?

[kendog]

I have a 94-1500 and I put brakes on the front. They didn't pulsate but I had just got the truck and figured why not put on some new brakes. I had the front rotors turned and when I put everything back together they started pulsating. I drove it for 2 days and then took the rotors off and took them to another auto parts store and they turned them and then they were ok, the guy told me sometimes if they cut them too fast they will warp. He also said that some of the brake pads are really cheap and they can also start to pulse and warp. Try taking them to another auto parts store.

[bwood]

The shoes and pads are NAPA premium parts. I've been using them for most brake jobs I've done and haven't had any trouble. I pulled the drums last night and everything looks ok, except the driver side axle seal is leaking and getting fluid on the friction surfaces. I degreased the drum and took some sandpaper and roughed-up the friction surfaces on the pads and drum. I think this is part of the problem, because the pulsating pedal calmed down until I got to work. When I got there the fluid made it back out on to the drum and the pulsating went back to the way it was. I called my GM service center since my truck is covered under a GM bumper to bumper warranty I purchased with the truck in May 02. I'll let them fix the seal and I'm going to replace the shoes since the driver side is possibly ruined from the fluid, and I'll take the drums to be surfaced.

[Stingray42]

Do you have ABS on your truck? If ya, then are u standing on the brakes? cause that will make the pulsating happen, doesn't sound like it, but just my 2 cents

[bwood]

The axle seals fixed it. They replaced the seals and roughed up the shoes and drums and now everything is smooth. I thought maybe it was an ABS issue so I pulled the ABS relay and fuse so the system wouldn't respond and I did some tests the problem still existed. But, for now, everything is working well.