2001 Jeep Cherokee Noise when braking, now noise and idle v

Had the transmission replaced about 3 months ago. Now when we were braking there was a sound coming from the dash - no other way to describe it than spinning a 50 cent piece on aluminum. Took it to a mechanic and he was stumped and possibly a vacuum leak.

All of a sudden it doesn't do it anymore but now it's idling strangely (skipping on startup) and sometimes when accelerating it sounds like somethings caught in the driveshaft or wheel (like a bad belt, stick in the wheel rim, it clicks VERY loudly). Also the temp is flying up to max when sitting at a red light. This will happen for a day and then be okay for a week. We only drive it about 10 miles a day so anything you would suggest would be helpful.

Thanks!