92 Ls400 Vibration At 70-80 Mph

[pishta]

Here are some pictures of my differential mounts... The two rear mounts and the mount on the bracket. The right side mount doesn't look too bad but the left side mount has a totally different appearance. I think the bracket mount is looking pretty shabby too. This is a 1991...

The pictures are pretty hi res, close to 2mb each. You'll need Acrobat v7 or later to open.

Any opinions on the condition of these?

Thanks

Shabby, is that huge void supposed to be there on the bracket mount? Ill look at my 92 and see if it looks any better.

[JimsGX]

Here are some pictures of my differential mounts... The two rear mounts and the mount on the bracket. The right side mount doesn't look too bad but the left side mount has a totally different appearance. I think the bracket mount is looking pretty shabby too. This is a 1991...

The pictures are pretty hi res, close to 2mb each. You'll need Acrobat v7 or later to open.

Any opinions on the condition of these?

Thanks

Shabby, is that huge void supposed to be there on the bracket mount? Ill look at my 92 and see if it looks any better.

Maybe not... Let me know what you find out!

[JimsGX]

Here are some pictures of my differential mounts... The two rear mounts and the mount on the bracket. The right side mount doesn't look too bad but the left side mount has a totally different appearance. I think the bracket mount is looking pretty shabby too. This is a 1991...

The pictures are pretty hi res, close to 2mb each. You'll need Acrobat v7 or later to open.

Any opinions on the condition of these?

Thanks

Shabby, is that huge void supposed to be there on the bracket mount? Ill look at my 92 and see if it looks any better.

Pishta,

Did you have a chance to check out your differential mount to see if that gap is there on yours like in the above bracket .pdf file?

Jim

[pishta]

Here are some pictures of my differential mounts... The two rear mounts and the mount on the bracket. The right side mount doesn't look too bad but the left side mount has a totally different appearance. I think the bracket mount is looking pretty shabby too. This is a 1991...

The pictures are pretty hi res, close to 2mb each. You'll need Acrobat v7 or later to open.

Any opinions on the condition of these?

Thanks

Shabby, is that huge void supposed to be there on the bracket mount? Ill look at my 92 and see if it looks any better.

Pishta,

Did you have a chance to check out your differential mount to see if that gap is there on yours like in the above bracket .pdf file?

sorry, not yet but Ill look at it tonight and get a pic if I can get under there. If you look at the high res photo of the "void" you can see a casting in the rubber that would not be there if it were a crack, well see. Looking back on these posts I see an entry that says the problem is on acceleration and not so much on cruise or decel. Long time ago, I had a pinion bearing in my differential go bad and that was the same symptom. On drive the bearing was pushed back on the good race due to the angle of the cut on the ring gear, when you cruised or decelerated the pinion was pushed forward against the bad bearing and made an audible noise. A cold bearing may not make the racket, but when it gets warm (hot) it expands and then gets noisy.

Jim

[JimsGX]

I've thought about that being the cause but didn't put it high on my list because of the mileage on the car (77K) and the fact that its been babied and received every service through Lexus. Still possible though. I would assume there are some shims in there as well that could be out of spec. If I have the diff oil changed again and check for shavings on the plug (magnetic I assume) or in the old oil, I might see something there. The oil was changed last at 65k miles or so. it was done at 30k too...

What made me curious about that mount was the gap that you observed in the picture. I assume at this point, because I haven't verified for myself, that the propeller shaft is turning counter-clockwise when the vehicle is in forward gear. This would keep pressure on that rubber bushing in forward, but during decel or coast, the pressure would be somewhat relieved and possibly allow that rubber bushing to vibrate a bit. Pure speculation at this point though.

Jim

[pishta]

Here are some pictures of my differential mounts... The two rear mounts and the mount on the bracket. The right side mount doesn't look too bad but the left side mount has a totally different appearance. I think the bracket mount is looking pretty shabby too. This is a 1991...

The pictures are pretty hi res, close to 2mb each. You'll need Acrobat v7 or later to open.

Any opinions on the condition of these?

Thanks

Shabby, is that huge void supposed to be there on the bracket mount? Ill look at my 92 and see if it looks any better.

Pishta,

Did you have a chance to check out your differential mount to see if that gap is there on yours like in the above bracket .pdf file?

sorry, not yet but Ill look at it tonight and get a pic if I can get under there. If you look at the high res photo of the "void" you can see a casting in the rubber that would not be there if it were a crack, well see. Looking back on these posts I see an entry that says the problem is on acceleration and not so much on cruise or decel. Long time ago, I had a pinion bearing in my differential go bad and that was the same symptom. On drive the bearing was pushed back on the good race due to the angle of the cut on the ring gear, when you cruised or decelerated the pinion was pushed forward against the bad bearing and made an audible noise. A cold bearing may not make the racket, but when it gets warm (hot) it expands and then gets noisy.

Jim

Here we go. As I suspected your "void" is engineered that way, see the casting mark I mentioned? As a CA car, mine is a little cleaner down there rust wise :-) But look what I DID find down there with the camera (shooting in almost total darkness with just the focus beam illuminating before the shot) Check out my driveshaft coupler. See the gaps between the Differential flange and the rubber coupler? I dont know if this is a flash illusion (flash is to the left of the lens as it takes a picture,so it would throw a shadow to the right of an object, the camera was upside down shooting this set of pics) or if the coupler is actually pulled away from the flange? Ill look again tomorrow in daylight/flashlight. Digital cameras are so cool....

[JimsGX]

Hi Pishta,

Its got to be the shadow of the flash on the camera. I can't imagine it being loose. Your car is very clean underneath compared to mine. The road salt around here can do a number on everything.

Thanks for taking the pictures to verify that mount. I've had three mechanics look at my vibration problem, including the dealer, and no one can do more than guess at what the problem might be. Replace this, replace that... I think at this point, I'm going to live with the vibration for awhile and see if it gets worse. If it does, it should be more easily identifiable instead of arbitrarily starting to replace parts. It really isn't all that bad, I'm just anal about this type of stuff. I'll track it down eventually. Is your vibration something you can live with? Did you notice it when you test drove the car? I didn't with mine, because it doesn't show up until after its driven awhile.

I had the oil (Mobil 1) and filter changed today, the differential oil, and the transmission flushed. There wasn't any sign of metal particles on the differential drain plug magnet or in the diff oil itself. Guess that's a good sign.

What's your next step?

Jim

[pishta]

Hi Pishta,

Its got to be the shadow of the flash on the camera. I can't imagine it being loose. Your car is very clean underneath compared to mine. The road salt around here can do a number on everything.

Thanks for taking the pictures to verify that mount. I've had three mechanics look at my vibration problem, including the dealer, and no one can do more than guess at what the problem might be. Replace this, replace that... I think at this point, I'm going to live with the vibration for awhile and see if it gets worse. If it does, it should be more easily identifiable instead of arbitrarily starting to replace parts. It really isn't all that bad, I'm just anal about this type of stuff. I'll track it down eventually. Is your vibration something you can live with? Did you notice it when you test drove the car? I didn't with mine, because it doesn't show up until after its driven awhile.

I had the oil (Mobil 1) and filter changed today, the differential oil, and the transmission flushed. There wasn't any sign of metal particles on the differential drain plug magnet or in the diff oil itself. Guess that's a good sign.

What's your next step?

Jim

Mine is to do a load balance on the tires on a Hunter GSP 9700 tire balancer (In widespread use today) . It uses a wheel to press onto the tire to simulate a load on the tire and then takes that measurement into consideration when balancing the tire. Looking into this I found a new Caddy CTX owner that couldnt get a high speed vibe diagnosed or corrected. He insisted that the dealership do this test and found that all 4 of his stock Continental tires failed this test! He got 4 dealer replacement tires from BFG (I think), they all passed and there is no more vibe, and of course a 4 wheel alignment so my steering wheel is exactly straight. After that its tie rod ends (could probably use them and they are cheap) and then a set of 200 dollar UCA's from Arnett. Its my wifes car so I dont drive it unless we are going somewhere so it bugs me far more than her.

[melon]

Sounds like they replaced the bushings and screwed up getting the drive shaft and diff back into proper alignment . By having it off center it caused a vibration and caused the ends to wear which is why it cannot be rebalanced.

I am a layman compared to the others in this thread.

But I am going to replace my rear carrier bushings soon as per the advice of a Lexus mechanic who looked over the LS '95 prior to purchase.

Based on this post, does that mean that if the job isn't done perfectly, then my car can experience some vibration issues? I don't like to bring my car to a dealer for budget related reasons, but is this a job that is best left for a dealer?

I had some bad vibration at 60 mph but replacing and balancing the tires fixed that, it appears.

[chrisnisbet]

Well, based upon my own limited experience, I'd say yes, things do need to be done carefully, ensuring that everything is aligned correctly. I'd be interested to know if you car suddenly develops a vibration after your work has been done. I'm not sure that a dealer will necessarily do a better job than anyone else. I guess they are more likely to know of the importance of doing the job properly though.