Is300h wobbles / shakes when on smooth roads

[Usmanbashir]

Hi all 

In need of some advice please.

On smooth road surfaces  I am feeling a shaking/ vibrating sensation through out the car mainly in the drivers seat and footwell whilst maintaining a steady speed or accelerating 40mph onwards. Not feeling this on normal roads. Can also feel the vibration through the gear stick if held. (Mildly) 

Steps taken to eliminate issue

replaced all 4 tyres balanced and 4 wheel alignment done by kwik fit

car has had a recent full service including all filters and spark plugs and rear differential oil

Any advice on troubleshooting or anyone experienced a similar issue will be greatly appreciated 

[IS300FSPORT]

Have you just purchased the car?

Or has it started happening after any mechanical work?

Start with the basics:

- Tyre pressures

- Check ball joints for any play including the control arm bushes 

- Sticking brake caliper or binding brakes (brake shoes) for the parking brake adjusted correctly

- Condition of your brakes 

- Loose wheel nuts (hope not)

- Worn shock absorbers (leaking)?

- Diff fluid was original Toyota/Lexus diff fluid used I.E correct grade & topped up to the correct level?

- Defective new tyre straight after a tyre change is suspect 

- Hit any pot holes? 

The list is exhaustive try to trace back before any work was undertaken.

[Notamech]

I think early model GSs and ISs had some drivetrain vibration issues. I think lexus had a software update for it not sure if it fixed the issue though. But as suggested above rule out the simpler things first.