Hi experts! As stated in the title, I'm getting a vibration in my rear end (ostensibly) that ONLY occurs when under very light load and at certain RPMs. I have no idea what is going on and when I am either not on the throttle or on it heavily there is no vibration.

To elaborate; the vibration feels like when you are in a car with 2 15" subwoofers in the trunk and it its a long low beat that rattles the trunk. I have a G35X 2008 with 75k miles on it. Any input is welcome!!!!

Thanks,

Chris

A symptom of a dying valve train (transmission) is the feeling and sound of driving over rumble strips usually between 45 and 60 mph.

Thanks! Danjetta. I hope that is not the case, but yeah it almost feels like rumble strips..... car doesn't accelerate obviously until i give it more gas and sounds more like a huge bass cannon but that is close. Do you know what it is that is failing and making the car do that around 1500 rpm?

Sorry, I meant valve body, not valve train. I've had a few of these go bad in my day.

Sounds like you could be describing a slipping transmission clutch and a slipping gear. An automatic transmission is an incredibly delicate system of valves, springs, gears, and passages – so any number of things could be causing the problem. The most common point of failure is usually a faulty internal component (such as a solenoid that isn't allowing fluid to access and properly activate a clutch pack).

Simple problems are low, incorrect, or old transmission fluid; more complex problems usually require rebuild or replacement.

If your problem is the transmission, I would have your shop do a fluid drain and refill – but beware that if you do have a more serious problem, swapping the old fluid may make your problem worse.

I would have a shop take a look. 75K miles is early for transmission failure on your car, so have them check your whole drive train.

Good luck!

Check the differential bushings under the car. Mine were shot and it felt like the car was always trying to move up a hill when getting started. After replacement, the car seems to drive itself away.