boatracer

I have a strange problem when I am going around 70 MPH and start going down a hill - If I just let off the gas and don't hit the brake or anything I get a vibration/shaking in the car between 60-70 MPH - as soon as I drop below 60 MPH the vibration/shaking goes away. I don't get it in the steering wheel but feel it in the car. I had the tires and alignment checked and they say they are all okay. Could this we a start of a drivetrain or transmission problem? I only get it when going down a steep hill between 60-70 MPH and let off the load of the car.

Haven't taken it to Lexus yet to get it checked out but planning on it. I just turned 100K on the car and it has been doing this since about 85K. It is intermitten so hard to pin down.

Anybody have any ideas?
thanks

Lexmex

I don't have any steep hills here per se (there's some bridges overpass that have somewhat decent drops), but I remember very well my Mexican experience (there's videos on youtube going well above those speeds) and I know that whenever I had some suspension piece on the fritz, it would get exacerbated at higher speeds. However, you go at lower speeds and you won't feel a thing and shaking suspension pieces by hand with the vehicle jacked up might not show anything because there's not enough force there.

I don't know how significant that shaking is, but if it's anything like times I recall it could be shocks, lower suspension arms, a wheel that is not quite balanced right, a wheel bearing, ball joint. Those are areas offhand that could throw enough force if it's not steering related.

Theoretically, you could jack up the front of the vehicle and see if anything is loose (shaking the wheel and shaking some of the suspension pieces).

The only thing of note with the transmission (and you can look at some of my 1/4 mile track videos on youtube under lexmex1) is right around that 70mph mark you will note the gears changing. I've noticed improved performance at the changeover after I've changed out my gear oil, but that's about the only other thing of note around that mph range.

JoeMonday

Hi my 09 IS250 is doing exact thing your car did. What was wrong with your car? Did you ever get it fix?
Thanks

salimshah

This is an old thread, so don't be surprised if no one answers. Have you tried the IS forum?

Speaking in generalities, what you are experiencing is when the wheels try to spin the engine. Transmission mounts and driveshaft couplings are stressed. Have them examined as they are best diagnosed with the vehicle on the lift.

Salim

bordenj66

Follow up Q’s:

Is your car FWD or AWD?

Can you describe how the shaking starts and progresses, and what you feel in the car?

Does the car pull to either side while the symptoms occur?

Does the car pull to one side generally, or while braking?

Is the steering wheel ‘loose’, meaning small turns of the wheel don’t actually turn the wheels?

Does the car make any clunking sounds when turning at low speeds?

Anything else worth mentioning?

Australian

The solution would have been control arms ball joints breaking all effect steering and suspension. Car is accident waiting to happen at this point. Probably smashed before traded or fixed since silence.

JoeMonday

I lifted the car up and everything under the 53K miles car should look like (nice & clean) nothing is out of the ordinary. Tranny mount, couplings, boots etc. Just took the car in, re-balanced all 4 wheels @ one the local tire shops and voila the shudder/vibration went away all together. I am so glad that it’s not something else. The car (Lexus IS 250) is now smooth and quiet as it should be.
I hope this will help someone else. Sometimes shuddering & vibrations can be eliminated just by re-balancing your wheels.

salimshah

Very true that vibration at 65-75mph can be due wheel balance issue. What threw me off was the reference to "when letting off the gas" in the thread title. Wheel balance vibrations happen even when you coast, speeding up and slowing down.

I am happy the problem is solved.

Salim