Bad Vibration When Braking?

[Berry]

02 silverado, 141000, 4wd, new rotors/pads front and rear, new tires, u joints good, shocks good. When slowing down (no braking) at 45mph I start to get a hum (much like a front wheel bearing) coming from the rear, braking amplifies it then around 20 mph I start getting the vibration (while on the brakes) I dont feel it in the steering but under my butt and in the pedal. Have had both front and rear rotors trued up and it still does it. I purchased the truck from a friend (original owner) and know that he has never had any bulletin repairs done to it. I Just did the I-shaft, I just cant seem to pin point this problem. Out of ideas. Can someone help?

[jrrod2004]

A couple of different things that may be the problem:

 

 

Subject:Loud Grinding Growling Noise from Rear of Vehicle after Hitting Bumps - kw GMT800 GMT805 GMT806 GMT820 GMT830 bind boom brake buzz chatter click clunk contaminated decelerate differential disc drum #PIT3060 - (07/09/2004)

 

 

 

 

Models:.

 

 

 

 

The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

 

 

Condition/Concern:

Certain vehicles may exhibit a loud rattle, grinding or growling noise from the rear of the vehicle. The noise normally occurs at low speeds, typically 30 mph or less, and is noticed when hitting sharp bumps. This noise may be coming from the parking brake shoes. If a rear axle seal has been leaking axle fluid onto the parking brake shoes and the parking brake shoes are retained by the original style retainer, the shoes may begin to oscillate inside the parking brake drum creating this noise.

 

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Recommendations/Instructions

Replace the affected axle seal/s, parking brake shoes, and install the updated parking brake retainer per bulletin 02-05-26-002a.

 

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

 

Models:

(99-03 Chevrolet All Full Size 1500 Trucks and Utilities) and (99-03 GMC All Full Size 1500 Trucks and Utilities) and (02-03 Cadillac All Full Size Utilities)

 

 

 

Bad Balance of brakes, etc.