How's it going all? After covid hit I stopped driving my car as much ( was driving it every day 100+ miles a day ). Here lately I have been noticing a distinct rattling/ knocking noise from what appears to be the drivers side while idle in park. When I'm idle in park it's very subtle but when I hold the rpm to about 1500-2000rpms it gets louder then goes away at higher rpm. I do have an axle back that could be drowning the noise out. Today I crawled under the car while my wife held it at 1500rpm so I can see where the rattle was coming from. I used the old broom stick trick and held it to the belly pan of the transmission and found the rattle there. Any one have any idea? My initial thought was the output shaft but the car is in park..

Any thoughts or ideas would help. Thanks!

 

It sounds like it might be your cats rattling internally?

 

That is possible. The car is a 2012 with 135,000 miles. The heat shield did seem a little loose but that would have been more of a metallic sound I would imagine. When I held my ear to the broom stick though it was on the transmission pan.

 

When I had the same noise you described it turned out to be my flex plate. It started out like that then got worse as time went on until it finally broke. Cost me $2200. Took about a year from start to finish. Not saying that's your problem though.

 

I'm worried it might be the flex plate. Was that sound happening in park though? I do a little bit of spirited driving and I have heard these flex plates don't like 1st and 2nd gear pulls.

 

Yes it was happening in park. The noise, i believe, is because the plate is out of balance and hitting stuff. I told my buddy who just graduated tech school and he asked me did i like to redline it using the paddles. I said yes. He said that's why. I would, on occasion, drive in 4th on the highway at triple digit speeds near redline. I guess all that heat from constant redlining is bad for the plate and transmission. The tech noted that the bearing and torque converter were stuck due to overheating.

 

Was there any performance issues that you noticed? I know the flex plates are notorious for cracking due to spirited driving. You can pick them up for cheap, $350 for an oem one. The problem is dropping the transmission to get it done.

 

Besides that very annoying noise, no. A short time before it broke I noticed dried up coolant around the expansion cap from where it boiled over. Then one day I drive about 40 miles in DS mode and I heard this VERY loud rattling. On my way back home it wouldn't go above 80 then 65 and it would "buck" when i gave it gas. Then maybe 4 miles from the dealer I hear this real loud bang and my engine and traction light come on and the car started bucking bad whenever I gave it gas and it would barely respond to the pedal. Last year I took it to the dealer and they said it was coming from torque converter area but I wasn't about to pay thousands of dollars at the time when the only issue was the noise.

 

So any updates?

 

Still rattling, a little more noticeable now, I'm back to some highway driving.

 

Would the rattle go away when you'd brake torque? I'm not 100% sure that it is the flex plate.

 

Don't know since I rarely ever did that. If it ain't the flex plate then what else could it be?

 

Heat shield (crosses fingers), spun bearing (dies a little bit inside). These cars are known to have rattles as a thread on here has said. I do know the flex plate is a common issue but I am bone stock with the exception of an axle back. I'd like to imagine nissan engineers would have designed that flex plate to handle the stock power of the car for some time..

 

I'm going to have to agree with iCrap on this one. I noticed the same sound under the same conditions as you described on my G. I did some investigating and found that when I placed my pry bar between the head shield on the down stream cat and the body of the cat itself, the rattling noise went away with little pressure. I removed the heat shields and found the noise to lessen significantly. I'm sure the substrate has just detached and is rattling around inside the cat.

My G has about 164,000, so maybe a higher milage issue? I'm also stock with a few extremely minor exceptions.

 

I thought this initially, but the noise was coming from the bell housing. I sold the car last week, prior to selling my wife was driving the car some what spirited and when we got home the noise was noticeably worse. I am going to miss that car but we need something bigger for a family of 4! I will definitely be back in something with a vq after the little ones get bigger.