Drove the car on the highway today for the first time above 80mph and I have the fluctuating vibrations that are felt under the seat (none on the steering wheel) for about 3 seconds, then not felt for another 3 seconds, then felt again for 3, etc etc. From searching, one thread suggested driveshaft but no confirmation on the cause. Another person fixed it with new motor mounts. Has anyone experienced this problem? Is it common for driveshafts to need replacement on these cars? It literally fluctuates only at 80mph and above. Not constant vibration that would be associated with bent wheels or bad/out of balance tires

 

...good luck. I had a dispute with Lexus over this exact issue, exactly as you described. Several trips to the dealer and a decent amount of money later I'm no closer to resolution. They told me I had "2 bent rims and worn tires" despite another dealer telling me my rims were not bent. I had them repair the rims and bought new tires, was okay for a month or so, had the same thing all over again today. I probably will end up looking further into this but as of right now I don't have much insight other than that.

 

Back when I first purchased my used IS350, I remember having a vibration at ONLY 70-75 mph. It ended up being a single bent wheel issue. Food for thought.

 

Im going to check the driveline and motor mounts next time I have it up in the air, as well as recheck the tires and wheels

 

Rechecked the balance. All 4 tires were out of balance, even though I balanced them very recently after purchasing the car. No wheels bent. Nothing abnormal seen in the driveline. I still feel the vibration - however, its more subtle than before. Because of this, and knowing the tires went out of balance quickly, Im going to attribute the vibration to bad tires. I wont worry about it for now unless the symptoms get worse, or until the tread wears down some more

 

I got all 4 new tires and I still couldn't shake the problem. I'm really frustrated with it, only happens around 70+, I don't really have an entire set of other rims to try but will try to look into it soon..I feel like I've felt the problem at idle though so it could be engine/trans mounts but I need to look into that further that might just be in my head since I'm always thinking about it...I also have read every thread on the internet, cannot find a common answer.

 

Exactly what tires might you have on the car right now?

 

use Michellin tires, those Performance and sport tires are noise and mile vibration, Lexus is performance car uses low profile sport tires, they are normal, just remember back in the 80-90s we rode 195/65/15, my friend owned a 2015 Mercedes C400 4matic V6-twin turbo, wheels are 225/40/19 front 255/40/19 rear, same vibration on freeway and his tires worn inward bad.

I had my cheap Chinese tires on my old RWD 350 , shake bad at 40mph and 62mph , switched to Mechellin shake gone ! you either go Mechelllin or Continental but Conti = expensive.

 

I would check the wheels and tires

 

I just put 4 new Continental DWS 06 tires on so the tires aren't the problem, infact they made the car feel MUCH better than the old tires on there so that was a good plus but the vibration was with both sets...I have the spare, might try to swap it around and see if it fixes anything, I feel a vibration in slow speeds too so I should be able to pinpoint which wheel. If I put it all the way around and still no solution then we have a much harder to find problem lol

 

Didn't you post this on the Lexus Reddit? This looks awfully familiar as I vaguely recall replying to it...

Did you ever get the tires road force balanced (specifically at high speeds)?

 

Michelin Pilot Sport, with alignment wear on the edges of the front tires (not bald). I corrected the alignment when I bought the car

I get no vibration at slow speeds. Just exactly over 80 MPH, comes, goes, comes, goes, etc...

Nope, wasnt me. I work at a shop so I use our regular balancer

 

Hmm... I have a similar issue. At higher speeds, sometimes I get vibrations... other times I don't. Seems to depend on which road I am driving on...

 

You wouldn't be the first member on here that I've read about having vibration and/or chunking issue while on those tires.

Let me guess, the innermost edges of the front tires are wearing more. That is due to the "soft" factory LCA bushing. There are aftermarket options available that are much stiffer (poly instead of rubber) that will eliminate that wear issue.

 

First thing you really should be mentioning is whether it is RWD or AWD. Front CV axles can start play a big part in weird vibrations before they officially feel like they are toast. And There is no reason to ever change a driveshaft, unless you hit something that smashed it hard enough to bend it in someway. However, the U-joints in that driveshaft could most certainly cause vibration issues. Easy enough job and fairly cheap parts. If it were me I would do that first just to see if it helps. You can inspect them first to see if it feels like they have play, but once again, you won't necessarily feel play right away once a vibration starts.