I have tried searching but have not found this specific problem.

My neighbor has a 2005 SBQC 4x4 with 60k, and has had the front brakes grab hard on the freeway without pushing the brake pedal. He thought it was de-rating the power at first, but when he pulled over the truck stopped without assistance.

I went out to see his truck and noticed BOTH front rotors had signs of aggressive braking. We put his truck on my lift and flushed all the brake fluid. He was happy as can be for about a week until the exact same thing happened again to his wife.

I am leaning toward a master cylinder since both fronts are braking equally, but wanted to throw it out here first. He talked to the dealer and they want to diagnose it, they say it might be electronic, and they need to see it happen. We all know how that goes.

Thanks for the help guys.

 

Sounds like it gets scared of going fast.
I would check and see if pedal can possiblly hang just short of full return.
If pedal does not fully return the compensating ports in MC will cause pressure to build in brakes. Is brake switch holding pedal applied?
Are you sure calipers not sticking? And it could be MC or booster.

 

Good suggestions, I pulled the MC and completely cleaned it out and inspected everything. All looks new now and truck drove fine, but time will tell.