rear end bouncing upon braking

[Boog]

My 06 GMC crewcab has about 136,000 miles on it. Since we've had it the wife has mentioned it sometimes feels like the rear end is bouncing when she brakes. I didn't feel it but I replaced the shocks anyway. It still does it and one day I was behind her and actually saw it bounce. Not extreme mind you but noticeable all the same. The truck body doesn't move but the rear axle takes quick choppy bounces right before the truck comes to a stop. The brake pedal does not pulsate like warped rotors would cause. The tires have been replaced and run out smooth. As I sit here and type this I'm beginning to think it is sounding more like the rear drums may need to be turned even though there is no pulsing of the pedal.
That's all I can come up with.
Any other ideas?

[1FastBrick]

Have you looked at the brakes at all???

Ever bleed the system???

I recently rebuilt a truck and the rear brakes were put back together with broken adjusters. It appears they fell out or were not installed properly by the last Shop. They appeared to have been ground down by metal on metal contact.

Anyhow I didn't realize the adjuster's were not functioning correctly. The brakes would not release properly and I would have to pull the drums back off. I broke a couple of wheel cylinder's until I figured it out.

1 other thing to check would be the leaf springs. Make sure none of the individual leafs are broken.

[69chevytrucker]

check for loose ubolts on axle my rear jumps on my blazer but my prob is the leaf bushings

[68C15]

disc or drum on rear?

Are front shocks weak letting nose dive taking weight off rear?

does it have a brake proportioning valve or is this done all with the ABS system?

[Boog]

I've pulled the rear drums off before to have a look but no brake work has been necessary yet. It is all stock. Shocks are fine and no nose dive on stops. I do plan to replace the pads, shoes and have the rotors and drums turned soon. This truck has the 4.10 gear and G80 by the way.

[dragginmetal]

Is it a 3500? I saw a bulletin for "Rear Axle Hop During Aggressive Braking". It was for 06-07 classic 3500.

[Boog]

It's a 1500.

[Boog]

Update.
I had the rotors and drums turned and put on new pads and shoes this week. So far it brakes real smooth. Have not felt that rear bounce so far. I'll hope this took care of it.