loulo

My problem is a little different. There is no vibration but a whup whup whuping noise that starts around 50 mph and increases with speed, it is loud enough to be annoying. it ssems to be coming from the rear under the car. Does this sound like a wheel bearing or something in thr differential.

PointABE

iTrader: (2)

Me too I have this same problem and have been wondering what the problem was. But my rumbling occurs between the 1.3k-1.6k RPM. I have a '92.

99lexusBC

I just bought a near perfect 1999 1-owner with 175k and all maint. records....etc...
I am experiencing the low rumble. (not too bad, but noticeable)

I have isolated that it happens when in park around 1500+ RPMs also when driving 45-50mph and again around 70mph. If I shift into N while going 45-50 it goes away so it is definitely not: driveshaft/u-joint, wheels/tires or suspension.

I am planning on replacing the trans mount and hoping that it will solve the issue!

I really hope it is not anything more serious.

I will post results once I have replaced it.

Thanks! I am looking forward to being a part of this excellent forum!

andyman32

Hallelujah!

I just wanted to post back here that I just replaced the transmission bushing. All the 'harmonic' rumbling is completely, 100%, gone. The car runs like a top and has no indication of any kind of pulse or rumbling in any of the former conditions that reproduced the issue, and nowhere else for that matter.

The old bushing was 'flattened' quite a bit, and even when sitting outside the car, appeared to be about 1/4" to 3/8" shorter than the replacement. It was also extremely "loose" - the rubber was very soft. So even though it was visually intact, it had in fact failed.

My guess is that rather than allowing unwanted vibration into the frame, the culprit for the rumble noise is more that the old bushing had pancaked to the point that the transmission was off alignment with the driveshaft by, say, 1/2 degree. It was probably doing weird things in the region of the output shaft bearings at certain engine speeds. With the new bushing, everything seems smoother and quicker - acceleration, up and downshifting, cruising.



So the lesson I've taken from this - and will pass along for posterity - is that if you're getting weird noise, rumbles from the drivetrain at certain road and/or engine speeds, and you have 50K+ miles on the transmission mount, just replace it. Start there, then proceed with the diagnostics. I started by replacing the transmission oil and filter, and was about to put in a rebuilt torque converter, but stopped short...

Anyway, this one was the culprit all along, the smoking gun, and if I'd followed the advice offered here sooner, I could have had this stellar-driving, supple-riding, silken-smooth car all along!

Happy 4th all!

deanshark

Yup, gotta listen when more then 3 people say the same thing. But, I'm glad ya got it fixed. I can only imagine how good it feels. (I gotta imagine b/c I need to fix mine) The tranny mount is one of the first things that people feel, and change, when buying a used LS b/c they all go bad too quick.

andyman32

I'm going to wager that it is the culprit. The symptoms are absolutely identical to my own, other than that in neutral the rumble occurred at 2000-2100 RPM, and at road speed it was worst between 45 and 50 mph. Those differences may be explained away in terms of how badly the old mount has failed and how compressed it is. I don't know which way - "more" or "less" - but one could surmise that the behavior might change a bit one way or the other based on the state of the mount.

Let us know if it worked for you too... I'll be interested to hear.

andyman32

Ha! Indeed! Not bad at all though, it's a quick swap-out and I sourced the new one for $35 delivered

I just wanted to make my point emphatically, for the sake of posterity: don't ignore the transmission mount!

I may also do the motor mounts at some point in the next couple of months, just as a matter of course. Ideally you'd do all 3 at the same time but the parts website sent the transmission mounts without the motor mounts that I ordered... and I wanted to put it in and see what happens... c'est la vie.

loulo

change your transmission rear mount, had this same problem, almost drove me crazy.