I’m stumped.. need help.

[70c10guy]

Hi everyone, never been In this section of the forum but seems like a pretty cool section. I’ve come here today to seek for help.. for a... ford. The truck is a 1997 f350 single cab long bed. It’s got the 7.3 powerstroke in it and e4od. Anyways, I got a brake issue. Every time I step on the brakes the rear left wants to lock up on me. It’s got. New booster, new master, new rear wheel abs valve, new shoes and hardware kit, and new wheel cylinders in the rear, and callers up front. I have the parking brake disconnected to rule it out.

The rear line is a single line that tees off on the rear axle and splits to each whee cylinder. I was thinking it was the brake hose. But wouldn’t both wheel cylinders lock up? Again, I’m stumped. I’ve given up, for now in putting time and effort into this pile... also no abs light on. The abs works when I stomp on the brakes but when I lightly depress on the brakes it wants to lock up. Super unsafe especially in traffic. But when I’m all alone on the road and decide to mash the brake pedal, it pulsates the locking up on the rear left. And when lightly on the brakes it does the opposite.. locks up. Hopefully someone’s had the same experience before. Hoping to get answers and fix this pig! Thanks, enjoy!