leaking wheel cylinder
it looks like a wheel
4 cylinder or 6 cylinder, 4 wheel drive or 2 wheel drive, need to know what you have cause they are all different. It is a 4 wheel drive, 6 cylinder.
Wheel cylinder stops would keep the wheel cylinder from coming apart.
Could be a bad axle seal Could be a bad brake wheel cylinder Could be a bad brake fluid line
Only other massive internal damage inside the brake drum could cause this. They do tend to wear out due to contaminated fluid or the vehicle being driven through deep puddles and contaminating the cylinder's.
Several things could be the cause. You could have an emergency brake not releasing. You could have a brake hose internally collapsed or a leaking wheel cylinder. A defective grease seal letting grease get on the linings are some possibilities.
Most likely it's a faulty ignition cylinder.
Tire out of balance is the most likely cause. Can also be a bent wheel.
Master cylinder possible but could also be wheel cylinder problems or warped rotors
You might be out of brake fluid. Our rear wheel cylinder was leaking and ran ours out of fluid and the light came on.
If the rear brakes are drum brakes, then there could be a leaky wheel cylinder. The wetness inside the drum will cover all the brake shoes and parts and cause the wheel to lock up when applied. The build of pressure could be due to the wheel cylinder leaking and causing a pressure loss, but rising when the brakes are applied or pumped up. This may/may not be your case, but definitely worth checking the rears.