Brakes locking up when cold....

My 1998 Astro AWD's brakes (not sure which axle) lock up first thing in the day when rolling from stop. Only happens a few times, or until I drive a mile or so. No matter how lightly the pedal is pressed, the vehicle stops hard and grabs.
Here's whats been replaced already: Rotors, Calipers, Pads, Both front hoses, slides are lubed and everthing is bled. Rear drums, shoes, all hardware and all bled there also.
I am pulling my hair out trying to figure this one out....any takers?

Does the van have an ABS system? Does it have an hydraulic power assist unit or vacuum?

All Astro Vans have power-assist, and yes, it has ABS. No codes or indicator lights in the ABS system

Yes they all have power assist. But which kind of assist is what BB was asking? Does it have a vacuum assist or hydro-boost assist?

Sounds like there might be some grease getting out of the rear axle onto the rear pads to me. Just something to look at.

It has vacuum power assist. No grease on any of the linings, they have all been cleaned a few times. ????

Thanks for the reply. I asked because about 1998-99 is when they were changed from vacuum power boosters to hydraulic assist boosters. Some of the early units had trouble with the valving/reaction mechanism and would "stack up" hydraulic pressure with no pedal input, resulting in locked brakes as you described.

It has vacuum power assist. No grease on any of the linings, they have all been cleaned a few times. ????

You can't/shouldn't clean brake linings with anything. Next time use masking tape over the linings to keep grease n stuff off 'em.

The linings are/were new, in "cleaning" them, brake cleaner spray (only) was used to eliminate any chance of stray grease on the surfaces, I am well aware brake linings cannot be "cleaned" conventionally.
I will further investigate the possibility of an ABS or proportioning valve issue. Thanks for your help.

The linings are/were new, in "cleaning" them, brake cleaner spray (only) was used to eliminate any chance of stray grease on the surfaces, I am well aware brake linings cannot be "cleaned" conventionally.
I will further investigate the possibility of an ABS or proportioning valve issue. Thanks for your help.

I was taught that was a no-no as well...

it could also be the adjustment plugs are missings which causes condensation to get in..
that may be your problem