So im finally getting the last parts of my car taken care of so that it has a 100% clean bill of health. Since I got my I30 its had a humming noise coming from the bottom of the car toward the front. Its a bit hard to pinpoint thats why im looking for help from anyone that might have delt with this. Seems to be loudest upon deceleration, between 40-50 mph. I have no noise at all when driving at highway speed or at speeds lower than 40. My best guess after some research is it could possibly be low trans fluid or old fluid in the differential? Also read that there is a common problem with axel bearings in the front end that can be the cause. Im hoping that its not the bearings since it seems very hard to fix without a professional. Also want to make sure that my tranny is not on its way out. Im less apt to fault the tranny really since it shifts smoothly with no grinds. Thoughts? Ideas? Experiences?


BTW im riding a 99 I30 limited with 157k

 

My only guess would be the tires you have. I have some really cheap tires on the front and it hums the loudest at about 30. Other than that I don't hear it. And from my experience, when the bearings go out, they make a high pitched squeak sound. But I could be wrong.

 

Interesting. that was my initial thought at first also but the tires are almost brand new and I had them balanced and rotated just to be sure and the sound is still there. I wonder if they are just cheap tires but ive never had such a pronounced noise with a tire before. To me is "feels" like something mechanical.

 

are you sure its not just the sound of your engine decelerating?

 

Yeah mine are newish and they were balanced and everything. And I also didn't have it until I got these cheap tires. And it probably feels mechanical because when you hear it, it probably sends a slight vibration through the car.. Just like mine lol

 

yes it does send some vibration through the car, I can feel it slightly in the pedal thats what worried me. I like this car but its seeming very hard to get it down to that whisper quiet sound that all my other Nissans have had. I guess the VQ has some natural decel noises that Ive never heard before? o well, Now on to that timing chain guide noise I guess. Obviosly im not about to tear into it but I heard that using a good thick oil can reduce the sound a lot. Right now since its super hot in FL I can get away with running some 10w oil for a while. This weekend I planned on swapping in some royal purple 10w-30 which is what ive used in all my other cars. Thoughts?

 

Royal purple is a synthetic oil. Do you leak oil already? If yes then it will get worse. Some people have even started leaking oil when they switched to synthetic when they didn't leak oil before.

I personally use 10w-30 in the summer and 5w-30 in winter.

 

Hmm. ive never heard of synthetic oil causing leaks like that. I have owned 3 Nissan before this one and Ive used synthetic in each one without issue, and I know for a fact 2 out of 3 of the previous owners didnt use synthetic, nor did they change the oil as religously as I did. I used royal purple in my s13 hatch for 3 years, you could have eaten off the inside of the motor it was so clean, and quiet. Anyway, what I was thinking I might do here is maybe go half and half with the weights since it seems that full synthetic 10w-30 would be too thick. Im thinking 2 qts of each should do good.

 

the vq30 is special like that. I wouldn't use two different weights...

forums.maxima.org/4th-generation-maxima-1995-1999/644416-poll-fully-synthetic-vs-conventional.html

 

It is either tires or outer axle bearing. Although the boot is not ripped like mine was, the bearings was humming at those speeds. Tried to save it by purchasing the kit from Nissan but to no avail. Just bought another OEM one and before I put it on, I bought the kits again from Nissan and will replace inner and outer boots before installing so I don't have to look at it again for another 5 years.