I just bought a 1999 SC300.
The car has a pretty audible humming noise when driving in top gear. The problem doesn?t occur in gears 1-3 (almost quiet as a whisper) but comes up in 4th (4-spd automatic).
I pretty sure there is a problem with the CV joints already (there is a pop noise when I turn the wheel after coming out of reverse) but I don?t think these two are in anyway related.
Any suggestions on what this could be?
Noises are difficult to identify without actually hearing them.
Check yhour tire pressure to make sure the tires are properly inflated.
Check the condition of the transmission fluid - is it brown or smell burnt?
Does the humming sound change if you are in 4th gear but tap the brake pedal enough to disengage the torque converter lock-up?
Does the humming change when accelerating or decelerating in 4th?
What road speed range?
What engine RPM range?
Your car does not have CV joints in the front so any noise comig from the front of the car is not from the CV joints. Could be ball joints, rack ends, control arm bushings, etc.
brake
Thanks for the response, Ray.
The tires are properly inflated and new.
The transmission fluid looks fresh. I?m guessing they replaced the transmission fluid at the dealership.
Actually, I did some experimenting and it?s not just in 4th gear.
It seems to start at almost exactly 40mph and stays for anything higher.
Acceleration/deceleration and engine RPM don?t seem to make a difference.
Might it just be normal roud noise from loud tires or coming from the suspension?
Several clues point to the tires as the cause of the humming.
First, the tires are new so they are the biggest variable in the car.
Transmission, engine, and driveline, bearing noises tend to change with engine RPM, road speed, acceleration, deceleration, temperature, etc.
Tire noises tend to become noticeable at a certain speed and road surface and stay about the same volume but may change in pitch with speed. Tires tend to be noisier on concrete surfaces than on asphalt surfaces.
There is a catch-22 when driving a really quiet car like the LS or SC, and that is that noises that might ordinarily be drowned out in background noise becomes noticeable.
You can confirm that the tires are causing the noise by driving on several different road surfaces, i.e., concrete, asphalt, gravel and see if the noise changes.
"thoffen" wrote: > I just bought a 1999 SC300. > > The car has a pretty audible humming noise when driving in top > gear. The problem doesn't occur in gears 1-3 (almost quiet as > a whisper) but comes up in 4th (4-spd automatic). > > I pretty sure there is a problem with the CV joints already > (there is a pop noise when I turn the wheel after coming out > of reverse) but I don't think these two are in anyway related. > > Any suggestions on what this could be?
That POP sound you hear is normal from every SC. Simplified: it?s the sound of the brake pads popping off the rotors when you change from D to R, or R to D. It?s completely normal, happens with every SC.
BTW I own a 1994 SC3, I?m just here on this forum for my Volvo, for Lexus forums I use
Edit, as for the tires, have them re-balanced at any discount tire shop, and see if that fixes your humming. :wink:
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