When applying Brakes I get a noise that sounds like ABS is engaging & I have no Brakes. This only happens @ very low speed 5 mph & engine idling.
That is exactly whats happening. They had either a recall (I think it was) or a TSB out on this. Look up Silverado/Sierra Low Speed ABS activation. If it was a recall bring it in…never too late.
Look for rust jacking of the wheel speed sensors.
This causes the wheel speed sensors to move away from the tone rings for the speed sensors. And this causes the ABS to engage at low speeds.
Common problem on GM trucks.
I drove a lot of suburbans and small school buses on Chevy or GMC van chassis of this vintage in heavy salt belt and every one of them did this. New parts would fix them but the problem always returned.
This type of wheel sensor stops working at 5 mpg. If one or more wheel speed sensor isn’t reporting accurately, the computer thinks it’s time to activate antilocks. If cleaning tone wheel and sensor doesn’t work, find out which sensor(s) is bad with scanner or take it to a parts store for a scan and replace the sensor(s).
Get a tape measure and measure the height of the front fender to the ground on each side. Compare them. Has one side sagged? If this is a 4wd, crank the torsion bar bolt a turn or 2 to raise the low corner of the truck. Test to see if the problem went away. This fixed the problem on my 04 truck.
If it is a 2wd the fix involves new front springs. Coincidentally, they sell a special set of springs if the drivers side sags 1/2 to 1 inch.
The ABS activates because the front tires are not equally loaded. Sagging springs causes that.