2002 Toyota Camry. No problems when I brake going forward, but when I’m backing out of my driveway and put on the brakes the rear ones squeal when pressure is applied.
I had my mechanic look at it and he says there is plenty of lining left, so I’m not sure what could be causing this. Anyone have any ideas? Is it something I need to worry about?
Thanks.
If it has rear disc brakes, it’s typical disc brake annoyance noise. You can almost certainly eliminate it by replacing the pads with premium quiet-engineered ones, and perhaps also resurfacing or replacing the rotors. The alternative is to live with it, which is much more cost-effective. 
If it has rear drum brakes, it may be from insufficient lubrication between the shoes and backing plates, or from glazing of the shoes and/or drums. For the former, lift the shoes off of the backing plates and apply high-temperature grease. For the latter, put a thimbleful or two of scouring powder (Bon Ami, Ajax, etc.) into the drum.
And either way, it’s not something to lose sleep over. If the components are in good shape and performing properly, it’s simply an annoyance.
Does the squeal happen only in the morning, after the car has been sitting overnight?
It might be occurrnig for a couple of reasons:
Often times, drum brakes self-calibrate when you step on the brake while in reverse. This can cause some unusual sounds. Since your brakes are used mostly while going forward, the pads have likely seated themselves into the calipers in such a way that when you go backward, they create excess noise.
In the morning, your brakes usually have a very thin coating of rust on them from moisture condensing on the brake surfaces. After a little bit of braking (usually braking from stopping at the end of your driveway will get most of it off) the rust will be scraped off. While there’s rust, there’s more noise than usual.
Gary, this is why you are one of my favorite posters on this board. I constantly am learning stuff. Ajax. Pure genius.