Brakes locking up

[Ttownmedia]

I have a 94 B4000. When applying the brakes, they apply normal then as the truck slows the brakes practically lock up. A couple of times I was just about stopped when wham, I was sent flying towards the steering wheel. All new front calipers and pads, whole system has been bled.
can this be a ABS problem? Or………. I don’t suspect a delaminated rear brake line.

 

[RonD]

Welcome to TRS

No, not ABS, ABS system reduces brake line pressure to prevent lockup

Take the truck to a gravel road and see which wheel is grabbing or if its both wheels on one axle

It reads like a new caliper or an old Slave cylinder is sticking
When you apply brake fluid pressure the caliper or slave doesn't move all the way out at first, it sticks, then when enough fluid pressure is added it suddenly unsticks and applies too much brake pressure

If its a caliper then you should feel steering wheel pulling to one side at first

Rear brakes have the ABS Valve which can get clogged, if both rear wheels lock up then that could be the issue, not the ABS system just its passage thru the valve

And its possible it could be Master or Booster, but you should feel pedal drop at the time of sudden harder braking