Brakes chatter when pedal pushed at any speed

high speed and heavy braking will produce a pulsation in the pedal
that is the abs working properly and the pulsations are the brake release and reapplying
intermittent abs light indicates a wire or wheel sensor problem at one of the wheels

Was your brake pedal on the floor or hard to depress? Your chattering might be the serpentine belt system. Remove the belt and test quickly again for noise, you will not have powersteering or cooling or charging systems, but you are just trying to pinpoint your chattering so you dont have to guess. You might want to replace your vacuum valve at power brake booster if your pedal was hard. It is a oneway valve that opens when the car gets turns on and pulls down a vacuum to assist the brake system. Sometimes the stick. If your brake pedal was on the floor, which I doubt at all, do not drive and seek professional help. Maybe your pedal assembly is coming loose and needs repinned.

Take it in to be check out,

Brake pads are eqipped with what they call "Feelers" these are metal tabs that will squeal or "chatter" when there may be a need for new Brake pads or rotor replacement or re-turning of rotors to their original shape and measurements.

Check brake pedal height, and see if pulling up on the pedal gets rid of the brake lights staying on.

Maybe the lines have to be bled to get rid of air in the brake lines.

Or, the rear brakes should be adjusted tighter.

If this is not the problem, maybe adjusting the brake light switch will help.

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ADJUSTMENT Dakota Models

1. Push and hold the brake pedal in the applied position.
2. Push the switch forward until fully seated against the bracket.
3. Release the brake pedal.
4. Lightly pull the brake pedal rearward until the master cylinder pushrod bottoms against its internal stop. The switch plunger is now set at its proper clearance.

1989-93 Pick-Up and Ramcharger Models WITHOUT SPEED CONTROL

1. Loosen the switch-to-pedal bracket screw and slide the switch away from the pedal arm.
2. Push the pedal down by hand and allow it to return on its own to the free-hanging position. Do not pull it back! Fig. 1: Brake light switch adjustment specifications - 1989-93 models
   
   
3. Slide the switch towards the pedal until there is a gap of 0.140 in. (3.5mm) between the plunger and pedal arm. NOTE: The pedal must not move when measuring the gap.
   
4. Tighten the switch screw to 82 inch lbs. (9 Nm). Recheck the gap.

WITH SPEED CONTROL

1. Push the switch through the clip in the mounting bracket until it is seated against the bracket. The pedal will move forward slightly.
2. Gently pull back on the pedal as far as it will go. The switch will ratchet backwards to the correct position.

1994-96 Pick-Up Models This procedure calls for setting the switch prior to installation. Installation directions are included in this one procedure.

1. Preset the switch in the following manner:
   1. Pull the switch plunger all the way out until it is fully extended.
   2. Push the switch plunger inward 4 detent positions (clicks). This will provide the preset position for the switch installation. The plunger will extend approximately 0.55 in. (14mm) out of the housing at this setting.
2. Connect the harness wires to the switch.
3. Press and hold down the brake pedal.
4. Install the switch. Align the tab with the notch, then insert the switch and turn clockwise about 30°to lock it in place. WARNING
   Do not use excessive force when setting the brake pedal switch or damage to the switch could result.
   
5. Release the brake pedal, then LIGHTLY pull the pedal fully rearward. The pedal will set the switch to the correct depth.

ABS------ Anti Lock Brakes will cause a chatter if applied with a lot of weight pushing it. An E350 is a big rig.
Might ask your Ford Tech about that possibility.

What you might be hearing is the solenoid that allows you to put your blazer in gear. It has a switch that is on the brake pedal, and that is why you can't put your blazer in gear without stepping on the brakes. If the brake switch is getting intermittent, you can get that sort of chatter out of it.

check for leaks on master cylinder if you haft to add brake fluid its definately leaking,throw out bearing maybe going out?may of glazed pressure plate? good luck!!

Bent disks or rotors. Who does the brake work?

Did you ever find a solution to this problem? My 2004 Colorado just started doing the exact same thing!

I can be reached at [email protected]

Thanks!