Odd thumping noise M35X, driving me crazy!

[mikew83]

There was an odd thumping noise that seemed to be coming from the front end when the car picked up speed. Especially around 42mph. Thump thump thump thump, etc. After discovering all 4 rims were bent from previous tires, I bought 4 new tires and 4 new rims for the car. The smoothness of ride has greatly improved, but alas this "thump" is still there. 2 different tire shops, and 1 Infiniti dealer have looked at the car. Nobody has mentioned anything wrong with the suspension,wheel bearings, or the new tires. Infiniti did have to replace spindles on 3/4 hubs due to prior aftermarket rims. Supposedly new rims were to solve this problem, as it was thought to be the bends hitting the road during rotation. Almost $2k later, I can't keep throwing money at this problem. Has anyone else had an issue like this? Maybe just a simple alignment?

My flanges at the Y-pipes have rusted out, and the car sounds like an FX now. I have occasionally noticed at highway speeds, the thumping sort of goes away when I take my foot off of the gas and let the car coast to reduce a few MPH. It's a moderate reduction, and it comes right back. Doesn't thump at very low speeds, and seems to greatly even out around 70-80mph too. I don't really see how exhaust would cause this, but I want to be as thorough as possible here

[Ilya]

Can you feel the thumping? Or is it just audible?

Hmmm...related to engine speed, etc. That's a tough one.

[mikew83]

I know! Trust me, it's driving me up a wall trying to figure out what it is lol

It's more audible than it is tangible. You can feel it "ever so slightly" but not really. The wheel doesn't shake. The only physical clue to it really, is my rear sunshade. It stopped working and is deployed about 1/4 of the way. When the car is driving, even on a freshly paved smooth road, it bounces up and down. But alas, you don't really feel it inside the cabin. I could have sworn you feel it ever so slightly in the gas pedal, but it could just be me reaching for anything other than the sound.

[TOMatBMR]

It could very well be a bad wheel bearing or other bearing, like differential, drive shaft carrier etc etc. Does it change with speed?

[mikew83]

It's really noticeable from 20-45mph. Then it smooths out and you don't really hear it once you're doing 70-80mph. That's why they kept telling me it was from the bends in the rims. Because the faster the wheel would spin, the more it would even out.

[mikew83]

I thought I would post the findings, in case it helps another member down the road!

So I did indeed have a bad right front bearing (which I sort of figured,) but that wasn't the cause of the thumping. At some point in time, the car had aftermarket wheels forced onto it. They did a ton of damage to the car. Ive already replaced one stud on 3/4 hub assembly's. As it turns out, when they were half-a**ing the wheels onto the right front, they somehow loosened the hub to the point where my mechanic was able to unscrew it by hand! Water got into the bearing/hub ruining it, and somehow fused the hub to the outer CV joint. The CV joint is of course part of,,,,, the drive-shaft, half axle, whatever you want to call it! So the thumping was actually the shaft banging up and down :P

Now I have to pay an arm and a leg to replace the right front half axle. At least my mechanic was nice and smart enough to use a Timken bearing. All of you seem to speak pretty highly of them for our M's, so I'm hoping it pays off.

So.... Over.... Fixing..... This..... Car.... lol

[Ilya]

Wow that sucks. Glad you got it sorted though.

[mikew83]

Thanks, IlyaKol! I'm currently sitting at the stealer, praying that this is it for the car! lol