1993 chevy 3/4 ton van brakes

my brakes work fine unless i,m trying to stop on ice. they lock up and i hear a noise coming from the passenger side rear it sounds like a louder than normal fuel pump also i hear a slight grinding or rubbing sound only under very low speed braking 10 mph or less also from said side of rear please help i have recently removed brake dust and did a spring job on both sides but problem persists shoes also seem in order however there was a very slight crack in the one shoe on passenger side

Is the cracked shoe on the right rear? If it is, then my bet is the shoe is likely the cause.
FWIW
YMMV

I have ABS on my 1994 Chevy G20 3/4 ton Van with the 4.3L v6 and when I first began resurrecting it from the dead (sitting in tow yard for 3 yrs) I checked the Brakes cause it wanted to park itself on the side of the road every time I stepped on the break pedal. I was un able to bleed the break on the front left side of the van nothing zip0 that's when I found this cover halfway hanging off the ABS system under the van on the passenger side about halfway down the body, its like a motor/pump with a valve body mounted on each side it had little pins protruding out of each valve and they could not be pushed back in so I got another complete unit from the junk yard cause dealer wanted $1200 and junk yard $100 put the unit in and bled the brakes works great till the replacement unit will pop a pin out causing the service engine light to come on if I try breaking when one or more wheels on the same side of the van are on slippery leaves on the brick roads. I can stop jump out and push the pin in and all is fine till the next time weird breaking system. That was a lot of work. So far I am out about $1200 in parts so far bringing it back to life now and getting ready to redo AC system oh heck i need tires too, a fool and his money and now the lack of it, it might be worth it if i could only get more than 10 miles to the gallon whatsb up with this v6 4.3L it must have been designed by an oil company lol

my brakes work fine unless i,m trying to stop on ice. they lock up and i hear a noise coming from the passenger side rear it sounds like a louder than normal fuel pump also i hear a slight grinding or rubbing sound only under very low speed braking 10 mph or less also from said side of rear please help i have recently removed brake dust and did a spring job on both sides but problem persists shoes also seem in order however there was a very slight crack in the one shoe on passenger side
Any ABS or brake lights coming on ??
If you hear electric pump motor noise and pedal acts strange or hard or kicks backup your ABS anti lock brake is acting up or bad.
Just for a test run out off road on grass mud or ice where there is no danger of running over or into anything unplug the ABS system and see if problem goes away.
Or get a ABS scanner or tester on it.