New belt chirp when coasting or slowing in gear

I took a 500 mile trip recently and came back with a new chirping sound whenever I’m coasting into a turn or slowing to a stop light in 3rd, 2nd, or 1st gear. It’s an old truck, but well taken care of. I’ve always had the habit of down shifting to save wear on brake pads. I assume it’s a belt slip, but I’m wondering which pulley would create drag when coasting in gear. Does anybody know?

1991 Nissan Pickup, around 205k+ miles

Possible brake pad wear indicator.

When were the pads/rotors last replaced?

That’s just it, I rarely brake. I downshift in a turn or coming up to a stoplight. My uncle taught me that. It’s not a racing shift, it’s following the natural RPM. I don’t hear the chirp if I actually brake with the clutch engaged. The pads and rotor are actually ok.

You could remove the belt and manually check each pulley for wear, including the tensioner pulley.
If the tensioner pulley is old it may have lost strength.

Turn the pulley by hand while applying side pressure. Listen for scratching noises and look for glazed pulleys.

Use a straight edge and make sure all pulleys are aligned. Don’t forget the alternator.

It is possible the noise only happens at a lower rpm.