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CanadaCraig

A Low Pitched Moan

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Hi Guys!! :)

Yeah - I know - I should just turn the volume up on the stereo. [so I wouldn't have to obsess over all of these noises!!]

Speaking of which...

My '93 LS has developed a low pitch moan. Not sure how to describe it - exactly. I can hear it while I'm driving at highway/freeway speeds. The car is fine while I'm maintaining speed or accelerating - but when I let off the gas completely [as one would as they approach a light or slower cars or whatever] there is a low pitched moan. Not sure where it's coming from - exactly - so I won't even guess. Don't think it's the engine - though.

Any ideas?!

Thanks

Craig!! :)

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I posted something like this a while back.

Turns out for me it was the differential. On the lift with the engine going, My mechanic and I heard the same drone that I had reported at hwy speeds. Very annoying. The diff turned out to be a previous repair done by the prior owner. It was a salvage part that i did not know about.

While in the rear end, I had him replace the knuckle bushings (split), axle boots (leaking grease a little) and the wheel bearing on one side.

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I stand corrected. The differential was not the direct problem. I spoke to a Lexus mechanic today and he cited that some older LS400's exhibit this "drone". I say drone because it was the term used in the mechanics service bulletin. It states that the low-pitched noise that emanates during highway speeds from the rear of the vehicle. Because of the low frequency and location, it is often hard to pinpoint where the noise stems from. I listened to the noise the first time with a friend and it appeared to come from the differential. Well we were close. The drive systems in some LS’s have a harmonic that develops over time. The only way to eliminate it is to replace the differential bushings (requires being pressed out) and the sub-assembly bushings. The whole operation is labor intensive to take at least 8 hours. The noise, if it is the case, poses now safety concerns but is essentially an annoyance.

I posed a question to him (about the main source of the noise being from the differential bushings) if we could only replace those. He stated that it is possible that it would to some degree but he could not say. A quote for labor and parts at $450 was given just for the diff bushings and at least double that for the whole thing.

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Hi pachocco1!! :)

Thanks for replying to my message. [i should have said that after the first reply - sorry about that]

It's good to hear that the infamous 'moan' or 'drone' isn't a safety concern. But it CAN be annoying. Trouble is - I tend to focus on this type of thing - instead of just ignoring it. [which is what I should - probably - be doing] The trouble with my car [if I can put it that way] is that it sat [from what I understand] for a month or two EVERY winter while the previous older owner headed south. The car - when I bought it - had a battery charger -which kinda makes me wonder if it didn't 'sit' even longer than that - each year. It's not good for any car to just 'sit'. Chances are - a lot of the cars bushings are drier than they normally would be. I've already had the sway bar bushing lubricated. [because they were dry and the source of a crunching sound when going over dips and speed bumps, etc.]

I'll be sure to talk to my dealer about those differential bushings when I bring my car in next month for it's 86,000 km service. [which is just an oil/filter change - basically]

Do you happen to know WHEN that service bulletin was published?! [what year?]

Thanks again.

Craig!! :)

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