Harmonic Vibration At 40mph In Ls400

[dery45]

This is wierd. When crusing at about 40MPH, trans in overdrive, there is a reveberating vibration and sound coming from (I don't know where). When I shift out of overdrive amd hold my speed at bout 40 it gets worst. Tires are pratically new, I just had them balanced. There is no pulling of the steering wheel. The vibration/harmonic and not coming through the steering wheel. I keep leaning towards something on the drive train or transmission. Maybe even an engine mount or something? :chairshot:

Can anyone help!!!

Thanks,

Brad

[aarman4]

This is wierd. When crusing at about 40MPH, trans in overdrive, there is a reveberating vibration and sound coming from (I don't know where). When I shift out of overdrive amd hold my speed at bout 40 it gets worst. Tires are pratically new, I just had them balanced. There is no pulling of the steering wheel. The vibration/harmonic and not coming through the steering wheel. I keep leaning towards something on the drive train or transmission. Maybe even an engine mount or something?:chairshot:

Can anyone help!!!

Thanks,

Brad

Did this ever happen before the new tires were put on or balanced? Did this immediately happen after the tires were put on or balanced?

if the change happened corresponding your balancing/tire install direcctly, than chances are it is related to that.

[SKperformance]

It is rpm speed related if shifting out of overdrive makes it worse. The rear end of the tranny is still spinning at the same speed so it has to be engine related. Start with engine mounts and idlers fan blades and harmonic dampener . Then make sure the engine is running right.

[dery45]

It is rpm speed related if shifting out of overdrive makes it worse. The rear end of the tranny is still spinning at the same speed so it has to be engine related. Start with engine mounts and idlers fan blades and harmonic dampener . Then make sure the engine is running right.

That makes plenty of sense. I was thinking it has to do with the engine or something in that area. I will have it checked out. Thanks partner.

[nc211]

What year is your LS? I ask, because there has been a documented history of a "drooning noise" problem from the rear, the differential mounting area that reverbs along the back crossmember and from there throughout the car's underside, primarily directly under you, and a little towards the back. I believe they addressed this with the gen 2 models "95+". My 95 had a little noise, but was eliminated with new rear differential mounts, altough I believe the third mount, which is the bolt on the passenger side that attaches up into the floor of the car, has a rubber insulator ring as well. I never changed that one, but it was on my immediate list, if I had kept the car.

There is a TSB out there for the droaning noise, I might still have it at home. But before i go hunting around for it, what year is your LS?

[dery45]

What year is your LS? I ask, because there has been a documented history of a "drooning noise" problem from the rear, the differential mounting area that reverbs along the back crossmember and from there throughout the car's underside, primarily directly under you, and a little towards the back. I believe they addressed this with the gen 2 models "95+". My 95 had a little noise, but was eliminated with new rear differential mounts, altough I believe the third mount, which is the bolt on the passenger side that attaches up into the floor of the car, has a rubber insulator ring as well. I never changed that one, but it was on my immediate list, if I had kept the car.

There is a TSB out there for the droaning noise, I might still have it at home. But before i go hunting around for it, what year is your LS?

It is Feb 1996

[nc211]

i couldn't find it in my pdf manual at home. however, i would start with the tranny mount first, which is about $26 bucks from parts.com, and very very easy to do yourself! That has helped countless people on here with vibration and noises from the driveline.

[eddielasvegas]

I'm glad you started this thread.

I have the same thing, but in the 43-47 MPH range.

Thanks for everyone's comments. I'm gonna try the tranny mount. ASAP.

Eddie