Hi, I bought my g35x sedan several weeks ago. It turned out that it shakes too much passing over the uneven surface and at high speed. I asked some owners and they told me it was normal. But I feel this TOO normal for me. Is there any way to make the suspension less "normal" and stabilize the car. I also went through a shock/strut stress test at two shops. First showed shocks were close to death, second showed they were OK. So I am confused. Can you help me?

 

If it's a vibration sort of feeling that gets worse with increased speed your tires might be out of balance, another possibility is the propeller shaft carrier bearing. Worn struts/shocks will make for a "squishy" feeling going down the road, sort of like you're floating rather than hugging the road, you will typically also start to hear the struts make a "clunking" or squeaking sound once they are completely dead. Sometimes there is oil on the piston shaft but not always.

 

Thanks for your reply! I have to explain more precisely: when I pass over a hole or an uneven surface I normally expect up&down movement. My case is left&right shaking. No squeaking sound at all. No oil on the piston shaft. Tires are okay. It might be the propeller shaft carrier bearing as you say so I will check it out too.

 

The propeller shaft carrier bearing would cause vibration that increased with speed. So what it sounds like you are experiencing is "body roll" where the car can LEAN to the left or right, normally the G is fairly planted but worn suspension components will definitely allow for a lot more roll. You can test the amount of body roll yourself by opening the driver side door and rocking the car by pushing on the roof where the door normally sits, I recommend opening the door first because it creates sort of a "ledge" for you to push on.

 

Exactly! The body rolls. Indeed I pushed it several times but with doors closed. Now I will follow your advice and will report right after. And yet how to define what component of the suspension failed or is about to fail.

 

It's probably just the struts, they lose the ability to control the dampening and rebound and the car feels like it rolls all over the place. You've already had someone diagnose the struts as failed, they probably weren't wrong but go to a reputable shop and get another opinion.

My self-test is to violently rock the car as hard as F'ing possible with the door open, when you let go of the car it should rock back to neutral position and THATS IT, if it continues to rock back and forth a couple times you have worn struts/shocks.

 

Thank you! I got it! I will test it the way you say although the car is pretty heavy. I also think It's probably the struts. Hope it will show what's wrong.

 

The test results are as follows: After a violently rock with two doors open at driver's side it felt like slightly rocking 4 times back and forth and then it stopped. It didn't stop at once and yet it wasn't that bad as I expected. Anyway next week I will replace the rear shock absorbers.
About the front struts - which ones to choose - coilovers or normal? The sport coil springs will lower the car which I don't want to happen. All I want is to stabilize it somehow and that's it. I gather, from the discussion I've been reading about the coil springs of the 2004 and 2005 models here, that changing of the springs should be followed by remaking of the sway bar and etc. So what am I supposed to do?

 

You do not need to replace the existing springs on the car, you can replace just the struts in the front and shocks in the rear. The front springs will need to be swapped from the old struts to the new ones and it requires the use of a spring compressor, typically folks just take the old and new set down to a shop and pay about $10 per spring to have someone else swap the springs to the new struts. The rear is a shock cartridge so it doesn't require anything fancy, just unbolt the old and install the new.

To expedite the process of changing the front struts some manufacturer's offer a "strut assembly" that comes with pre-installed new springs, you pay more for them since you are also buying a spring but the advantage is you don't need the spring compressor or shop to do it for you. The downside to the strut assemblies is you aren't guaranteed what springs they're going to use, sometimes the spring rates are different.

For a budget strut I would look at the KYB Excel G, you can pick up the complete set for around $250 usually.

 

Damping. Dampening isn't a thing .

 

I bet I can find it on the internet.

Damping sounds like I'm trying to make something slightly wet.

 

It's the opposite of what you think. Dampening is getting it wet. Damping is slowing moving !

 

OK, that's what I am going to do next week and I'll certainly get someone to fix it.
No, I'll only change the struts and the shocks since I don't have to change the springs.
Yes, I have already bought KYB Excel G rear shocks and I will put struts from the same brand in front.

However there is another problem occurred - a rattling noise at cold start. The mechanic said it was the oil filter, because it wasn't an original one and the chain was not getting oil during the start. I've replaced it with an original one but still have the same noise. Any ideas what this might be?

 

There's quite a few things that can rattle on the G35 but if it's DEFINITELY coming from the timing chain cover your tensioner might be wearing out. Fortunately there's an access cover in the timiglng cover so it's an easy repair. There's also a chance the tensioner guide is broken though and that requires removal of the entire cover which is basically disassembling the front of the engine.

If it's not coming from the timing cover then inspect the exhaust system especially the catalytic converter heat shields. Exhaust components wear out and start rattling until they get hot and expand.

 

No, I am not quite sure if it's coming from the timing chain or not. Luckily I haven't heard it for the last two days. However it's good to know that it would be an easy repair if it's the tensioner and hope it won't be neither the tensioner's guide, nor the catalytic converter heat shields.
I am changing the rear shocks soon and I will inform you about the results. Thank you so much for your help!