I had a shudder once that I couldn't trace down. Eventually opened up my locking hub and it was bone dry and covered in a fine dust of rust. Cleaned that up and sprayed it down lightly and life was good.

 

Well they said all the front bearings were shot, so they replaced those and also turned the rotors, the shuddering is gone but i still have to stand on it to get it to stop.

 

The following are causes for hard pedal

• No assist from the brake booster. The vacuum operated brake booster may be defective or not receiving a sufficient supply of vacuum.
• Brake linings contaminated with brake fluid, oil, or grease. The contamination reduces the stopping ability of the brakes.
• Worn brake linings. Severely worn brake linings have a greatly reduced stopping ability.
• Glazed brake linings (overheated). Brake linings which have been severely overheated (cracked, shiny, charcoal like appearance) have a greatly reduced stopping ability.
• New brake linings not seated. Newly installed brake linings require a break in period of approximately 50 miles. Until the new brake linings are properly seated, overall braking performance will be less than 100%. Braking performance will gradually increase as the new linings are broken in.

Check for proper brake booster operation.

• With the engine "OFF", depress and release the brake pedal 4-5 times.
• Depress the brake pedal firmly and start the engine.
• If the pedal goes down slightly the brake booster is operating properly.
• If the pedal does not go down slightly the brake booster is not assisting in brake operation. Verify vacuum supply to the booster.
• Maintain pressure on brake pedal while turning "OFF" engine. The pedal should remain in the same position. If the pedal slowly slowly rises, the booster or vacuum check valve is leaking. Replace as necessary.
• Verify the brake booster vacuum line is intact and installed properly. Verify that the vacuum check valve allows flow only towards the intake manifold, and not in reverse towards the booster.
• Verify that engine vacuum is at least 17 in hg.
• Inspect brake linings for sufficient thickness, contamination, and evidence of overheating. Replace as necessary.

(Above from service manual)


Keep working through it. These truck are noted for brakes that are not 'best in class'. but if you make sure that all lines are bled - including the RABS, that all cylinders and pads are good and make sure that the vacumn/booster is working. If the proble persists - I am scratching my head a little. Something somewhere is not quite right.

Good Luck