Ive been hearing some grinding noise periodically in my Z for a little while now and its starting to annoy me but I'm not sure what it is. Its always when I'm off the throttle.. usually when I accelerate and then let off the gas and roll and slow down you will hear a grinding noise similar to say.. a screw against a grinding wheel or something, it will last for maybe two or three seconds then go away but it damn near happens often.. more so when I have the car in "manual mode" and let off the gas.

At first I thought it may be the rear brake pads ( seems to come from the center or back of the car.. I cant quite pinpoint it, tho its not from the front ) but I just did the brakes and the noise persists so now I'm worried its the transmission.. but not sure if its normal and she's just noisy or something may be wrong. The car runs and shifts perfectly as if nothing is wrong however.. its just that noise.

 

i have a similiar problem except when mine sounds more like an electric engine when my foots off the gas and im idling

 

That's really weird... when was your last transmission fluid change? Do you know if there is actually the OEM Nissan fluid in it? How about the rear diff? Check all oil levels...

Any recent mechanical maintenance or repairs done? Check those areas first...

If your mechanically inclined i'd lift up the car and start checking things... make sure the drive shaft is tight and the diff is tight in its mounting. Then if everything feels tight check the axle shafts and finally wheel bearings / hub assembly. For some reason when you say it is only when not on the throttle and slowing down, I think torque converter...

If all that checks out could be brakes (check to make sure calipers are on tight) or suspension related, like bushings or shocks. Could be motormounts too possibly... this is all speculation until you start checking things, its just a process of elimination.

There is info on how to check a lot of these things in the FSM if you spend some time to look around.

 

I know its not the brakes or suspension as I just recently ( sunday ) changed the brakes and put coilovers on and the noise is still there, so I can eliminate that much. I'll check fluids. I hope its nothing major like the torque converter or diff. My uncle is the manager at a shop so I'll go and have him check it out on the lift. The car only has 43k miles and started doing this around 40k or so but is functioning like the day I bought it. Also the noise seems to only happen when the car is warmed up. If I start her up and drive around, you wont hear it at all until maybe 15 minutes of driving.

 

Yeah that's not gonna be fun it if it is something major.

Let us know what you find... i'm curious now.