ABS quick fix

I had a Jimmy start the old familiar low-speed ABS growl we all know so well and the MTG-2500 showed a drop out of the left front sensor at less than about 7 MPH. I went to change the sensor out for a used one from a failed hub. (I keep these for lots of reasons, like to rehome the motors when one sensor is bad and the test won't go) Anyway, pulled the sensor out and there were two of these spacers I'd never seen before; between the hub and sensor. I left them out and there was no interference between sensor and ring so I put it all back together again. The problem was and still is gone (over a week). Anyone else ever seen this?

They are stainless steel shims that are used to position the sensor to obtain the proper air gap between the sensor and the tone ring. Some vehicles have shims and other don't. Tolerance differences in the hub, tone ring and sensor determine what shim is used, if any.

There's alot of heat generated, and those shims might help keep the wheel speed sensor (WSS) from heat damage

The usual issue with this is rust build up under the sensor on the hub causes the sensor to pull slightly up from the tone ring, this can cause the drop out at low speeds, GM had a recall for this issue some time back, they cleaned up the mounting area and used a insulating grease around the area.