Pull to LH or RH, while braking:
Is mostly associated with. Brake front rotor disk runout, out of spec. We call this warped rotors. This can happen for a number of reason. First being poorly manufactured rotors. Cheap Chinese rotors are the worst. It's more often uneven deposit of material on disk rotor surfaces. Which is mostly causes by, uneven bedding in of pad material on disk surface. The cause, could be one's side rotor disk had oil on it. Can also be, built up of rust on the surface disk surface. Then when driven and bake, result in even bedding in. We can also cause runout issues, by ride brakes overheating. Then come to stop hold foot brake on. Oftentimes, re-bed corrects.
Bedding in:
Drive at 35 to 45 MPH, brake slowing to 15 to 10 MPH riding brakes. Repeat three to four times, without coming to a stop. This results in very hot pads and rotor disk surfaces. Which we must not stop, with foot brake on. Or we'll get a hot spot, were pad stops on disk. Use E-brake to come to stop, that last 5 to 0 MPH shift to N, the last ~2 down to 0 MPH. Let brakes cool down before driving again. Avoid hard stops or heavy braking for next 500 miles. Never use brakes to control downhill speed speed.
Rotor disk Runout:
Is checked, with a simple dial gauge. This should be checked. With every rotor change, even new OEM. FSM, has turn rotor and check at all 5 lug positions. Then turn to lug position that yield best (lowest) runout. Then mark wheel hub to rotor position, with match marks. Thereafter, when rotor removed. We place back at match marks (best run out). Whereas this is doable on rears. The fronts with our wheel hub assembly, it's not practical.
Machine brake rotor disk surface:
We can have rotor disk machined (turned) on a bench lathe, while they're off vehicle. Best, is to have "turned" on the vehicle (OTV) with and OTV brake lathe.
Turning rotor on the vehicle, especially with front wheel hub assembly. Is best! It trues rotor disk to the vehicle, yield the best runout. Turning corrects runout and variation in thickness between inner and outer disk surface (parallelism). Wheel bearings must be tights.
I've correct a lot of pulling and bucking with my OTV. Even junky Chinese rotors, can be trued to get silky smooth braking..
Squeal has gotten worse. It occurs when traveling at moderate speeds 30 - 40 mph. Never at higher speeds. It usually will occur after 10 mins of moderate driving. The sound is similar to a humming / squeal of rubber rubbing on its self.
Never replaced R&P bushings
Try coasting down hill 30-40MPH in N, engine idling. This helps eliminate engine & transmission sounds, from possibilities. BTW: Most bearings ie. U-joints (AKA spiders), axle bearing, wheel bearings, etc.. Tend to make an oscillating sound, when dry (lack grease) and or going bad.
Also press on brakes lightly, to see if sound changes. If so, likely brake issue.
One I've heard at low speed. Is axle needle and brass bushing. Likely making sounds at all speeds, but background road noises override at higher speeds.
Squeal:
If related to braking, is most often associated with wear indicators. They come in contact with rotor disk, when pads are at limite. Which is about 1mm pad remaining. We can sometimes hear this while driving and not even braking. The pads should pull away from rotor disk, enough so wear indicators don't touch and squeal.
So often brake services, are done poorly or wrong. Their pads end up ride on disk. So we can also get "Squeal", while driving. Which I find, so many are not serviced correctly. Typically we hear a change in squeal sound when braking, indicating a brake related issue.
Rear brakes serviced improperly, is very common. Number one, boots of pins not replaced. Bad boots, result in water entry into pins/mounting plate. Pins may then freeze. List goes on. Not installing fitting kit, rust fitting kit or no shims or incorrectly installed.
Fronts also have service created issues. Number one, is no outer shim or not clip in caliper pistons and locked onto pad with fitting kit. Sometime, anti rattle spring on wrong, rubbing on disk.
Pulling excessive, on road crown:
Pulling excessive, on road crown (not while braking). Which may also squeal, during turns and or in a dip. Is mostly associated with bad ball joint(s). Bad ball joint(s) can result in a pulling, during braking also.
Early stage, bad ball joint: Look close and you'll see lower (steering knuckle) move up just a tad, before any movement in LCA. This is ball moving up into socket of ball joint.
Late stage, bad ball joint: Click to open video. In this bad ball joint, ball very appeatly moves up into socket.
Bad Ball joint lower 99LC 268K - https://www.youtube.com/watch?v=znGVjxGw5_8
So often I find multiple issues.
Squeal, not only when driving. Very often is, we have bad serp belt or T-belt bearings.