LexRexBlue

A couple of months ago I noticed a strange hum at 45 mph when the car was coasting--not at braking or acceleraating. First they said it was the brakes. At 67,000 miles I didn't really know. They were changed. It wasn't the brakes. The noise was still there. The mechanic rode in the car, climbed in the back of the RX and listened more. He determined it was the Differential. They ordered and changed the differential. The noise was still there only now it was at 30 mph only. Then they said it was the bearings. They changed one side. You guessed it, the noise was still there. They didn't even bother to return the car they ordered the other side. Now the car has been returned and it seems ok. I'm almost afraid to hear the noise. Anyone else experience this on a 1999 RX 300?

RTIS250

iTrader: (9)

Ive heard of this issue before.. its actually usually not the bearing itself, its the dust shield behind it. But its common practice to replace the bearing at the same time. Usually a simple squirt of bearing grease in there will stop the noise.. but whenever i come across the problem, replacement of the part is the first thing we do. I hope all those parts were replaced under warranty and you didnt have to pay for it all... good luck with the car, hope its trouble free from now on

LexRexBlue

After 2 weeks of driving I've concluded that the hum is still there, but at 25 mph coasting--not accelerating or braking. They have no clue as to what it is. Any other suggestions?

RTIS250

iTrader: (9)

Could possibly be cupped tires... what brand of tires are on there?

LexRexBlue

They are Michelin Cross Terrain. They have been on the car almost a year now. What are cupped tires?

RTIS250

iTrader: (9)

Cupping is an irregular wearing of the tires... usually you can run your hand across the inner edge of the tire, or across the entire tread and feel a wavy pattern in the tread, instead of it being perfectly round... I would assume the tech who worked on your car would have checked for this, as well as tire pressures. These are things i usually look for when i hear this particular concern.

LexRexBlue

Thanks. I'll make sure they check when I bring the car in on Thursday. They are supposed to have a diagnostic mechanic drive with me to hear the noise. Would the sound from the cupping occur every time I'm at a specific speed, or just some times? It only occurs at odd times including every morning.

VVT-i

You may need to ask them to check the exhaust hanger or exhaust pipe. You may backed into something and slightly bend the exhaust pipe a little bit, enough for the exhaust pipe to tough the body or some part of the car and make this humming noise.
I don't know what else can make this humming noise beside Differential, wheel bearing and cupped tire. They did everything they could, except checking on the exhaust hanger or the tow hook on the right rear by the muffler.
You can ask them to rotate the tires from back to front, test drive the car and see if the noise goes from back to front. If the noise still in the back , then it's not the tires,not the rear diff, not the rear wheel bearings, because they already replaced them. Ask them to look at something obvious under the car. For example, bend exhaust pipe, bend heat shield, or any under body covers that not in place and touching the body of the car.

LexRexBlue

Thanks. I'll print this up and run it by them. Fortunately, they are very nice at the Lexus service. If I wasn't planning on giving this car to my son to drive I'd probably just let it go since I have ordered a new one--even if it doesn't come until April!

VVT-i

Cool.. . So, your new one is the Hybrid RX400??.

LexRexBlue

Ah Yes. The new car is supposed to be the hybrid. I'm hoping it'll arrive in Feb. instead of March because my son will be pressuring me for my car. I saw it at the Lexus Taste of Luxury, but I wonder how it will drive. I'm not so confident that this whole process will work out smoothly.

LexRexBlue

The car was checked "cold". They heard the noise and now they believe it is the transmission! I hope this is it. Meanwhile I'm happy to drive a new RX loaner.