This can be a normal situation or mechanical problem. Some brakes had natural squeal regardless of pad life or lubricant used. However many brake systems have squealers which make a sound alerting the pad life is at replacement stage.
The brake pad "squealers" are telling you to have the brakes checked.
I believe your 4-Runner has an option of either rear drum or rear disc brakes. If the squeal is coming from the rear and you have rear drum brakes, have them cleaned and adjusted. If the squeal comes from the front, a shim may have slipped off of one of the brake pads and is scraping on the hat of the rotor.
in VW's when you have the breaks adjusted out too far they tend to grab when reversing. There is an auto adjuster in the rear drum to keep your rear brakes adjusting. If the brakes are worn out they will "hang up" after reverse and cause squeeling.
In my 1999 Alero, it did this and it was traced back to the power steering pump going bad.
Bad Brakes are the first thing to check for. Modern Brakes Pads are designed with an extra metal clip attached to the pads, the clip has only one purpose, They squeal to let you know your brake pads need replacement.
There are three primary causes for brakes to squeal when applied. 1. Most often brake pads and rotors become glazed from continuous heavy traffic stop and go driving. Glaze can be removed with light sanding of the rotor but that is only a temporary resolution. If you continue the same driving habits, it would be wise to invest in ceramic brake pads. 2. Most cars and light trucks come from the factory with metallic bonded brake pads that have a wear indicator made right into the pad. When the pad needs to be changed it will squeal. And yes, brand new brake pads can squeal but that is largely caused by #1 glaze. 3. If you hear a squeal and a metallic grinding noise, the brake pads are completely shot and the caliper is doing the braking against the rotor. A brake pad that has worn this far has caused caliper and rotor damage. At this point the entire brake assembly will need replacement. Depending on the vehicle this could cost anywhere from $300 to $500 per wheel at a shop, and that translates to $600 to $1,000 for new front brakes only.
squeal is a lose belt or one of the accessory will need to be replaced soon
No they are quiet animals and will freeze still. If threatened they will show their claws and hiss. Only babies squeal to call mom for help.
Dirt, heat, or possible worn or glazed. The squeal is actually the brake pad vibrating very fast in it's mount on the cpliper. The real only way to get rid of it is to disassemble the caliper and install a vibration barriers between the caliper and the pad. There are many form of these vibration dampers,,,paper, spray . pastes...etc. The Papers seem to be the most effective in my own experience.
These creatures are very vocal. They will squeal at all kinds of things. It will not be a bad thing if it squeals like this if you know there is nothing wrong with it.
Loose belts
Belt may be loose or glazed