[shorod]

I had a fairly similar experience on my dad's 1997 S-10 with 4WD. His ABS seemed to only act up when he was in 4WD. Of course, here in Iowa, when you need 4WD, it's often a time when ABS would be most beneficial. On his truck, "act up" meant the ABS seemed to release the brakes when nearly to a stop.

Last Fall we heard a bad bearing in the front so I ordered a new wheel bearing assembly to replace it. The bolts were not loose on his, but the following Winter there were no ABS issues like the past several winters. The bearing was not noticeably loose, even with the wheel installed and off the ground. We only replaced it due to the noise it was making, but apparently it was loose enough to cause a similar issue to your bearing assembly that had loose mounting bolts.

-Rod