(Strange that the Make and Model boxes don’t seem to work in Linux)
For a while now when I stop (dry or wet pavement) just before stopping the brakes chatter and feel like they’re slipping. Our (current) mechanic says it’s an ABS thing, which I believe, but figures it will cost c $1000 to fix.
Anyone else have any suggestions? Or reliable troubleshooting tests?
Is the ABS warning light on?
Tester
Nope. No light
They just did callipers and pads in front, and that the rear drums seem fine.
The wheel speed sensor is part of the wheel bearing assembly.
https://www.rockauto.com/en/moreinfo.php?pk=3984273&cc=1442109&jsn=484
If the wheel bearing is starting to wear out, the speed sensor can become misaligned with the tone ring in the bearing, causing the ABS to engage at slow speeds.
Tester
Thanks. That sounds more likely. I’m thinking I may have found the limits of our latest mechanic. 
If the tires are in good shape and properly inflated, find a shop who knows how to test the wheel speed sensors. That’s the most likely reason for an ABS failure like this. Did this problem start happening immediately after replacing the calipers and pads? If so, might be a good idea to try having the system bled again. Generally that requires an ABS compatible scan tool to do correctly. The bleeding process requires certain valves in the ABS to be programmed opened, the closed in the proper sequence. It’s also possible the ABS unit was damaged if the shop forced brake fluid back from the caliper into the ABS when they pushed on the caliper pistons. They are supposed to open the bleeder valve first, so the fluid goes out that way, and not into the ABS unit.
The ABS issue predates the brake job. I optimistically assumed they would fix that as well as the brake issues.
No harm being optimistic. But caliper and pad problems don’t usually affect the ABS operation. The inputs to the ABS are the wheel speed sensors, and the outputs of the ABS are the hydraulic pressures to the calipers. A shop with the proper tooling can easily verify if the wheel speed sensors are working or not.