I have a 2004.5 LLY D/A Crew Cab 4x4 with 10k miles. Yesterday while driving in traffic in the rain, I had to hit the brakes hard to avoid another car that pulled out in front of me. I felt a slight vibration in the brake pedal, and heard a faint groaning noise. The truck drove fine afterwards, and the brakes performed without incident afterwards.

Is this normal? This is my first truck with ABS (and my first diesel), so I'm still very much in the learning phase.

Thanks in advance.

Bud

Yep, that's normal for ABS.

The ABS computer monitors the wheels for zero speed in a heavy braking manuveur. Wheels that have no rotation when braking hard indicate skidding. So, the ABS system reduces the hydraulic pressure on that wheel until the wheel starts to rotate.

Ideally, the brake system should maintain the hydraulic pressure just before the threshold of skidding. That would me the max braking force the tires/wheels/ brake system could produce.

In the early days of ABS, GM would just brake either the rear or front hydraulic circuits. Now, the systems are complex enough to control each wheel.

Thanks!

the same noise happens routinely when I brake hard. Esp if the road surface is not dry . . . .