Read drum brake help

[Shmee1984]

He all. New to the site. Got an issue I can not diagnose. Truck is a 95 K2500 with the 8 lug, 13 inch brakes with the 8600GVW. I have a BAD hop under heavy braking coming from the rear. Cant feel it in the steering wheel or brake pedal, but you sure feel it in the seat. I've replaced wheel cylinders, shoes, drums, all adjusters and springs, shocks, bled the system, etc. No brake or ABS light on the dash is on. I've disconnected the ABS fuse. I have it narrowed down to the rear drivers side. I can pull the wheel and drum off and back in the adjuster. No hop. Once the self adjuster starts getting back to where it should be, it starts hopping again. Been trying to fix this for over two years. Its driving me crazy. Any help/tips/info would be greatly appreciated.

 

[Shmee1984]

Should also mention that I have new tires and the wheels were balanced. I cant see anything wrong with the leaf springs and the bushings on them appear ok.

 

[evilunclegrimace]

Mount the brake drum on the axle inside out and spin it by hand with a dial indicator on the braking surface and see if you don't have an out of round drum

 

[shorepatrol]

Had the same problem. I replaced everything including rubber brake line and wheel cylnders. Problem solved lol

 

[Shmee1984]

Mount the brake drum on the axle inside out and spin it by hand with a dial indicator on the braking surface and see if you don't have an out of round drum

This was going on before I put the new drums on. The new ones didn't change anything.

 

[Shmee1984]

Had the same problem. I replaced everything including rubber brake line and wheel cylnders. Problem solved lol

I did the wheel cylinders. I'll try the rubber hoses next!

 

[Jglew82]

Experience has taught me that just because you purchase a new rotor/drum, doesn't mean it isn't warped. Id check that drum for warpage first.

 

[Shmee1984]

Experience has taught me that just because you purchase a new rotor/drum, doesn't mean it isn't warped. Id check that drum for warpage first.

This is true. I'll run it in and have them check it on the machine.

 

[CrustyJunker]

I'm going to bandwagon this thread late, too. I bought brand new drums for one of my little cars, bought good name brand (Raybestos), and one was worse than the junk one I took off! Very out of round out of the box. If I remember correctly, one old stock made in Mexico, the other was made in China. The Chinese one was horribly out of round. First I thought maybe I contaminated it with something... But it was just junk. I guess I was only out $12 or so since the car was an old GM product.

Just letting you know because it's new doesn't mean it's good! Our trucks are getting older, if it's not a performance replacement part, a lot of this stuff has been outsourced and the quality just isn't there. I can say the same on steering/front suspension parts and sheet metal/body panels for our trucks.

 

[Jglew82]

^^ yep. Any time I get new rotors and/or drums, I chuck them up on the brake lathe and give them a quick pass to check, and if needed go ahead and true them up.