Hello,

On my 2002 IS300, I'm hearing a squeaking type noise which sounds like something is swinging back and forth in the rear of car. Happens when going up a hill or turning. Seems to happen more after the car has just started and usually goes away after driving a while.

I also occasionally hear a fairly subtle creaking type noise underneath the car when braking (I suspect this one may be hard to diagnose over the internet).

I'm wondering if either of these sound urgent, or if I can wait until my next minor service to get this inspected.

 

Squeaking usually involves plastic / rubber components - so you could have some bushings that are old and dried up. Get a friend to ride in the back and see if he/she can tell what side it's on. At least knowing which side can help on where to focus.
Or if it's a higher pitched "squeak" it could be something like a heat shield rubbing on the frame. Heat shield is easy to narrow down - get under the car and just give a little tap on all of them and see if you hear a similar noise or notice if any are starting to fall off.

As for urgency.. if it gets louder and more frequent than that would mean something will be grinding or breaking soon.