98 Ls400 Severe Rear Vibration

[fjstl]

I searched the threads and couldn't any issues similar to this one.

My car has 150000 miles and while while driving this week, I experienced severe rear vibration. I thought I had a flat tire and checked it; turned out that the rear snow tires were fine. I then proceded to about 65mph, when the vibration occurred again. I then droved it to the Lexus dealership. They said I needed to have the rear brakes replaced - a lot of rust and pads wearing unevenly. They replaced rotors, pads, and shims. Drove the car 10 miles and the vibration occurred again. I returned to the dealership and they balanced all 4 tires. The mechanic said that the snow tires, which are General Altimax Arctic, are a softer compound and when driven fast could cause the tire to come out of balance for a few minutes. I then brought the car to where I purchased the tires, and they said the tires are fine. Tonight, while driving about 20 mph, the vibration occurred and did not end until after about 5 minutes, when I stopped for a few moments. The trani seems fine, but the vibration continues even after taking my foot off the gas pedal.

Has anyone experienced this or have a solution. The dealership is clueless.

[SRK]

I'd swap wheels and tires - either front to rear, or put summers back on. The vibration is apparently road speed related, and that usually means tires. No tire shop will admit their tires are bad.....

At least it won't cost much, if anything, to do this check and properly either identify or eliminate tires as the source of the problem.

[fjstl]

I'd swap wheels and tires - either front to rear, or put summers back on. The vibration is apparently road speed related, and that usually means tires. No tire shop will admit their tires are bad.....

At least it won't cost much, if anything, to do this check and properly either identify or eliminate tires as the source of the problem.

for what it's worth, I duplicated the problem starting directly from my driveway today. It started from 5mph and continued right up to about 40, where at that time I had to slow down. I drove to a mechanic who I use for my other cars and he rode with me and the same problem continued. He believes that a brake calipre is hanging but couldn't determine which one. The trani brackets, drive shaft, bushings etc., all check out to be ok.

[curiousB]

SRK makes a good point. Moving or changing wheels to see if the problem moves with the change will let you know if it is the wheel/tire or something fixed (bearings, brake drag, bent hub, warped rotor,....). At least that way you're narrowing down the things to check further.

I did have a case many years ago where a tire broke a cord(s) and that made it vibrate like crazy and they couldn't fix it by balancing. A new tire and all was good. I don't think it is a common failure but maybe worth checking into.

[fjstl]

SRK makes a good point. Moving or changing wheels to see if the problem moves with the change will let you know if it is the wheel/tire or something fixed (bearings, brake drag, bent hub, warped rotor,....). At least that way you're narrowing down the things to check further.

I did have a case many years ago where a tire broke a cord(s) and that made it vibrate like crazy and they couldn't fix it by balancing. A new tire and all was good. I don't think it is a common failure but maybe worth checking into.

as it turns out, according to the dealership, the ebrake components have to be replaced - at their cost - since they are causing havoc with the calipre. I hope this resolves the problem.

[SRK]

The ebrake is unrelated to the wheel caliper assembly. As a check the wheels can be spun when jacked up off the road and the drag on each corner confirmed. The caliper can be unbolted quickly to see if the ebrake is in fact dragging. Easy diagnosis, which seems to have eluded the dealer.

[fjstl]

The ebrake is unrelated to the wheel caliper assembly. As a check the wheels can be spun when jacked up off the road and the drag on each corner confirmed. The caliper can be unbolted quickly to see if the ebrake is in fact dragging. Easy diagnosis, which seems to have eluded the dealer.

I believe this can be closed out. The dealer replaced the complete ebrake assembly and seems to have resolved my problem. Thanks to everyone for their advice.