1999 Ls400 Rumble/moaning Sound

[pushrod]

Hi everyone,

I have just bought a 1999 LS400 with 89k, full lexus history. Car goes great, but at 70 mph in top gear (around 2000 rpm) the car develops a lowish harmonic moaning sound (not as high pitched as typical transmission whine). It sounds a bit like tyre rumble over a poorly surfaced road, but it does not seem to change on different surfaces and is not present above or below that speed. Levels all seem OK.

Has anyone else expereienced this problem or have any ideas as to what it might be? Could it be the exhaust?

Thanks for any help.

[benfur]

Hi everyone,

I have just bought a 1999 LS400 with 89k, full lexus history. Car goes great, but at 70 mph in top gear (around 2000 rpm) the car develops a lowish harmonic moaning sound (not as high pitched as typical transmission whine). It sounds a bit like tyre rumble over a poorly surfaced road, but it does not seem to change on different surfaces and is not present above or below that speed. Levels all seem OK.

Has anyone else expereienced this problem or have any ideas as to what it might be? Could it be the exhaust?

Thanks for any help.

Hi and welcome to LOC

Could be a wheel bearing

Try to establish which side, or front or back of car, noise is coming from

good luck hope its not to expensive

Benfur

[ROYT]

Also check back axle oil.....

[pushrod]

This sound has been getting worse, and Lexus couldn't find anything wrong with the car. I took it to an independent specialist who said he was pretty much convinced it was the tyres (Michelin primacy HP). In his opinion they were not suited to the car and he suggested the Dunlops that the car came with originally would be a better bet.

Other reports I've read of these tyres have been mostly favourable, has anyonoe else experienced similar issues?

[Haylands]

Hi

Is it engine speed related or vehicle speed related, does it do it at 70mph just in top gear?

What happens if you change down a gear with the gearstick?

Pete

[pushrod]

Hi

Is it engine speed related or vehicle speed related, does it do it at 70mph just in top gear?

What happens if you change down a gear with the gearstick?

Pete

No, it doesn't change irrespective of engine speed or higher/lower gears and the pitch of the noise stays the same.

[Haylands]

Hi

Is it engine speed related or vehicle speed related, does it do it at 70mph just in top gear?

What happens if you change down a gear with the gearstick?

Pete

No, it doesn't change irrespective of engine speed or higher/lower gears and the pitch of the noise stays the same.

Hi

In that case it has to be the drive train somewhere, a bearing, propshaft rubbers, rear diff bearings, etc

I had a similar noise on an old car and it turned out to be a buckled wheel, so the thoughts of a tyre or wheel maybe the first place to look, also are any of the underguards on the car loose, just one screw missing is enough to make them shimmy at speed.

I know you mentioned the exhaust so I presume it sounds like it comes from under the car but could it be something like the sunroof seal, try pushing against the sunroof and see if that makes a difference, same with the doors..... or ... could the exhaust be just touching the body somewhere and at a certain speed it vibrates and puts the noise through the car. Give it a wiggle and see if you can hear it touch the body.

Things like this are annoying but I'm sure if you work through it you will get there in the end...

Keep us posted

Pete