When I slow down, why is there a noise coming from the rear tire as if something rolling in the wheel or tire?

Your correct, It isn't the engine. I would start with the brakes, maybe wheel bearings, Axles. If front wheel drive, Lift the front tires off the ground and run it. If the noise goes away, look towards the back. Check the front bearings with the tires off the ground. Grab top and bottom, Wiggle the tire. Any movement the bearing is bad.

Try gently "weaving " back and forth while you can hear the noise,if it's worse turning one way than the other,figure on a wheel bearing,if it doesn't change,it's a tire . Rotation may calm the noise down and give you some more tire life.

Check rear brakes and that also means the emergency brake shoes that are located under the rear brake disk . and also check the rear shocks

Hello: Raise up the side (front or rear) the noise is coming from roll the wheel and wiggle from side to side. Any movement and or noise would indicate a failed wheel bearing.

does it get louder above 45-60mph? and much quieter at low speeds. It could be wheel bearings, a rear differential or front differential. If its a grinding humming noise its wheel bearings, listenin to see if theyre coming from the front or rear, left or right, or both when your driving to know what wheel bearing are bad. If its a whinning noise, its probably a differential. check and listen to hear if its coming from the front or rear. Also, check for loose plastic around the wheels. Lastly check your tires for uneven or choppy wear. move your hands front to back on the top of the tire. does it feel really choppy and rough, maybe you just need new tires

Based on your description: 150K+left rear slowed down much quicker than the right +/ and the humming noise, there is a great possibility that the Wheel Bearings will have to be replaced.

WHEEL BEARING USUALLY STARTS MAKING A ROARING TYPE NOISE WHICH USUALLY GETS LOUDER THE FASTER YOU DRIVE, SOMETIMES THEY WILL BE LOOSE , TO CHECK JACK UP THAT WHEEL AND GRAB TOP AND BOTTOM OF TIRE AND SHAKE, IF THERE IS MOVEMENT, TRY TO GET SOMEONE TO ROCK TIRE FOR YPU AND WATCH WHERE AXLE GOES INTO CENTER OF BEARING AND SEE IF AXLE IS MOVING WITH TIRE MOVEMENT AND SPINDLE REMAINS STATIONARY, THEN IT IS BAD BEARING, OR SOMETIMES THERE WILL BE NO MOVEMENT, THEN BLOCK REAR WHEELS AND RUN CAR WITH THAT WHEEL IN AIR AND SEE IF YOU HEAR NOISE, GOOD LUCK.

If it sounds like a rumble from back wheels it may be the rear end going out. Mine has been replaced twice with used rear end. You should be able to confirm it by looking at the rear tires both sides of tire for an oil leak or wet spot on tire or rim.

It could be a unevenly worn tire or a bad wheel bearing.

sounds like c/v axles (front drive shafts) they will make a clicking sound normally when turning sharp and accell at the same time at slow speeds / look at the axle boots and look for grease on the inside of the front wheels leaking out the axle boots