1 wheel locks up when breaking help!

Bad drum, grease on drum, bad hub all will cause lockup especially with rain or other wet conditions. It doesn't sound like you have entertained bad hub mounting. I assume you have outboard drums. Jack up axle. Loosen nuts 3-4 turns. Release and reapply parking brake then retighten lug nuts. Sometimes this will center drum on a worn hub. Otherwise centering sleeves to center drum on hub or replace hub with a new one.

 

Lets take this apart. You put brake shoes on this truck and now the brakes lock up on one wheel. You swapped service lines side to side and it still happens. You swapped slacks side to side as well. The way you have it posted the problem stays at the same wheel. Thats the way I'm reading it anyway. That means the problem is at that wheel and not on the service air lines.

So is the parking brake fully releasing? If it is then move closer to the wheel. Are the new shoes the same side to side? Is the drum correctly installed? Did you clean the mounting surface so that all parts are running true? Are all the return springs in place and working right? I think thats the problem personally. If all these pass muster then you are left with the S-cam or the spider.

 

Replace the brake chamber. Simple to do and really cheap. We've had a couple bad ones recently less than a year old and the parking brake spring breaks and doesn't allow the s-cam to return fully. This caused the brake to apply more pressure than normal when you pressed the pedal.