95 blazer brake problem

Have a wierd brake problem and hoping someone can help. Sometimes, but not always, when I apply the brakes, it feels like the brakes don't engage well and when I apply more pressure the brakes suddenly grab. Pedal feels like there is a rachet-type effect. Thought one of the front calipers was sticking. Replaced both front calipers and pads and problem still exists. Also replaced brake fluid and bled all 4 wheels and there is no difference. Tends to occur after truck is driven for a while and warms up. Any help is appreciated. Thanks.

Hopefully when you performed the swap, you gave everything a good wash of brake cleaner when done. Any contaminants, like caliper grease, brake fluid - your fingerprints even; may cause what you are describing. Check the caliper pots too for any signs of leakage, and mind fluid levels...flush and air-dry all exposed parts you can get with a quality brake cleaner and see if it helps. Dry any rubber boots and seals you splash with cleaner with a rag quickly. Some flushing solvents will rot rubber.

Check to see if the brake fluid is up to the proper level and check if there is any vacuum leaks from the brake booster.