2013 AWD 145K miles, car drives smooth at speeds below 60MPH but at highway speeds it develops a pretty annoying shake that is pretty variable in when it shows up and how bad it is. I can feel it in the seat, floor, pedals, and steering wheel. I assumed it was bad balance or tires so I had the wheels balanced, no change. Needed new tires so I bought a new set of Continentals, another balance, and an alignment. Vibration is the exact same. I decided to move my wheels front to back just in case the shop didn't rotate them around with the new tires, again no change. So this past weekend I got all 4 wheels off the ground and gave the suspension a good look over and pried on the bushings. Nothing was obviously worn but my shocks/struts could probably use a replace.

Having exhausted my personal knowledge of vibration sources, google turned up a driveshaft issue on AWD models and TSB ITB11-019. These stories seem to be more subtle vibrations that mainly show up in the rearview mirror, my mirror is perfectly stable while my *** and feet feel like I am in a cheap mall massage seat . The service stops for 2011 models so wondering if the issue lingered to the end of the run and if so do my symptoms seem worth it to purchased the TSB parts ($65) to try and fix it? My next step is to take it to a shop which I always try to avoid.

 

Did they check the wheels for runout when they balanced them? I know you tried rotating front <-> rear, but it's possible you have multiple bent wheels. These Enkei alloys are pretty soft.

 

Get under the car and look at the drive shafts. Make sure the bushings on each end do not have cracks on it. Also see if you get any movement out of them.

 

A late follow up on this, I have focused on getting the 260z back on the road.

I took it to a different shop and told them I think one or more wheel is bent. They didn't actually check runout but said they spun them each several times and couldn't find any that looked bent. Not sure how much I trust that evaluation but they are a reputable shop. I called around and only two shops (wheel repair) said they could check runout but are asking $200 to check all 4 not including any repairs.

I will see if someone local can let me try a set of wheels on.

Nothing with the driveshaft seems worn or loose.

 

Well I ended up doing the rebro service today and it made no difference so on to the next thing.