Sorry if this was mentioned and I missed it...

Have they checked the balance of your driveshaft yet?

 

Tahts what sucks about taking your car to the dealer/mech. You drive your car all the time and notice when there is a difference in the way it feels. They hop in and it feels fine cause they didnt know how it drove before. Hope you get it resolved.
PS ^ what Aeson said Id check the driveshaft also

 

No they have not. I mentioned that to them as well and they guy said ya ill check it all out...not.

Who else can check that besides a dealer? Can any repair shop check it?

 

There's no way it's the bearings right? I mean when i jacked up all the tired and grabbed and 12 and 6 there was no play at all.

 

To be honest, with such symptoms, I would first suspect a dent in one of your rims or a busted tire.

I would go as far as to swap wheels with someone without these symptoms first before I even think of those other issues. especially in such a young car.

Its ironic, cause I just troubleshooted the same issue on my car. I isolated it to the front right rim. I swapped that wheel with my summer wheel and the problem went away. There were two visible dents on the inside of the rim

in my experience, the G35 bearings make a loud howling noise (like a jet engine) at speeds above 50mph when they are ready to go.

you can isolate the noise by makes left and right lane changes on the highway. If the noise is exacerbated when you turn left, then you know the issue is on the right side and vice versa.

 

See i have had 2 different places look at my rims and both said they were fine. My local guy that i go to for everything said he tried to see if there was any issues with the rims or tires (old tires) and there was nothing.

It's just strange that it happened with my old tires and new ones. it's also weird that almost everyday on the way to work it's fine(except vibration in both seats) but as soon as i leave to go home, both wheel AND seats start to vibrate. It comes and goes. A bent rim i would think would happen all the time no?

It seems as if i try to take as long as possible to reach 75 mph on the highway, they doesn't vibrate but they still do. But if coming off the on ramp at a fast speed and getting up to 75 really quick, it will vibrate a lot. It's so dam strange

 

did u try the D to N scheme(not sure if its safe but most ppl think so) to see if its the tranny?

 

Not yet..i am nervous haha

No i plan on it tomorrow on my way home from work..there was too much traffic today to try it. It doesn't feel like the tranny other than the vibs in the seat but even those don't feel like tranny..but at this point the problem is probably right under my nose and i couldn't be more lost!


I just don't want it to come to the point where i am forced to start to try and replace different parts to fix the issue :\

 

^ i understand which is why you must first try to isolate out some of the major more expensive parts out of the way and then if need be you can trial and error with some smaller cheaper parts. I do recommend like another member said to try and get another set of rims(all 4) that you know are ok and not bent from a friend of yours and try if that fixes anything.

Vibrations caused by wheels can be hard isolate and fix until u are certain its because of them. If that checks out and the tranny is fine then it could be your mounts or maybe even the steering rack.

 

I have a plan right now. Going to put it in N tomorrow when it's happening if there is no traffic. That will rule out engine/transmission. I plan on having my local mechanic look at it on Tuesday. I am going to write a list of things i want him to check. It's just weird that it's in the seats and wheel. It would be so much easier if it was just 1 of those... So far i have:

CV Joints
U Joints
Brakes
Drive Shaft/half shaft and its balance
Engine mount
Trans mount
Rims/Tires
Steering


He will only charge me $40 bucks to look over that list on my car and i know he does good work. If he can't find anything..then i will break down and cry...lol but i really will...

Is it bad i want him to find something? lol I don't know anyone with 17's that can switch them to my car so that won't work

 

my ex girlfriend is having nearly identical problems with her 03 mitsubishi eclipse. i changed the front brakes twice, the rear drums, checked the bearings, had the tires specially balanced on a "roadforce" machine and even got her replacement rims....unfortunately nothing helped. i also had it down to the same list you do because it's all speed dependent. my mechanic friend also suggested checking her tie-rods, which i have not yet done. it is maddening because i cannot find it either. i want to change her tranny fluid since she has 150k miles, i'm wondering if that's part of the issue (as in not enough fluid and getting vibrations at high speed from lack of proper lubrication).

 

If all else fails, you can test your car on my OEM 17's

 

Well i narrowed down at least one thing today..it's not drivetrain related as i put the car in N when it was happening...slight seat and wheel vibrations and it still happened..passenger seat actually shook more in N.

Bringing it to my local guy Thursday and he is going to look over everything i have on that list.

What's even more strange? It barley did it at all today. I went home at lunch to grab something and it was only doing it a slight amount in the wheel..at other points i had it to 80 and it was fine...way back to work it was fine besides a few rough spots. Left work to come home and it was vibrating like usual but for only maybe a mile then it stopped...drove an exit past my usual one to try it out longer and was good up at 78 and pushed it to 85 and wasn't that bad

Makes it so much more confusing when it happens one day..and the next it barley does it watch tomorrow it will be terrible again..ahh!

 

Gremlins? is it temperature/weather dependent?

 

Well the high temp so far since i got the car has been 60..it was 52 yesterday and it did it like it usually does which is a lot. Today was colder and it barley did it so i think i ruled out temp as well as drive train. Weather wise, it still did it in the rain and on a clear and sunny day.

So no to weather/drive train..2 down..29 more to go LOL