I am Sam

Ok I have been chasing an annoying noise on my Z for awhile now and it has me stumped after all the things I've replaced. Originally when I bought the car I was having a clunk from the rear when shifting, I figured diff mounts or trans mount. It ended up being the diff clunking, but I wanted to do a poly transmission mount anyway so I replaced that as well. After installing the poly trans mount we noticed a tapping sound mostly at low speeds when you blip the throttle. It sounded like the drive shaft and my mechanic's first thought was u-joints. We took off the stock drive shaft and the u-joints were worn and the drive shaft was binding somewhat, but it wasn't horrible. I went ahead with a Z1 motorsports 1-piece aluminum drive shaft replacement though, because the u-joints, as you know, are not serviceable on the stock drive shaft. Well after replacing the drive shaft I noticed almost no difference. We decided to ignore it for now because we were going to pull the trans next and do a full clutch kit on the car.

Well then while we were replacing the clutch my mechanic buddy noticed my stock flywheel was pretty torn up and he suggested that could be the culprit. We figured my noise would probably go away with a new flywheel. So now I've got a brand new lightweight flywheel, stage 1 clutch, zspeed HD slave cylinder, new master cylinder, and new throwout bearing/pilot bushing of course. After that we put the stock trans mount back on just to see the difference. I didn't notice any noise at first because it is much quieter without the poly mount but sure enough, it was still tapping. The next thing I did was replace the motor mounts with poly mounts and put the poly trans mount back on.

Now the sound is much more audible again, I don't think it is an internal transmission noise because the lwf chatters like crazy but the poly mount puts all that sound into the cabin and you don't really hear it outside of the car unless you stick your head underneath the car. But this metal tapping sound I hear is quite noticeable from both in and outside the car. You can hear it the best if I'm in 1st gear at say 1200 rpm then I give the car like a quarter throttle and quickly let off you will hear "tap tap tap tap" like something metal is hitting against something else. It will also do it even worse if I down shift and rev match poorly. I.E. giving it 1000 more rpm than needed when I let the clutch out the car will buck a little and you will hear the tapping several times. Also to note; you don't hear the sound if you go over a speed bump in neutral or with the clutch in, even if you are going somewhat fast. So I don't think it's anything in the suspension. However, you will sorta hear it if I am in gear with the clutch out and ride over a speed bump, but it is not as noticeable as when I blip the throttle at low speeds.

Anyway, I tried my best to explain it all. I can provide more details if needed. We'll get the car back on the lift next week and take a look but I'm hoping someone can point us in the right direction so we aren't guessing anymore. I'm almost certain it's coming from around the transmission/drive shaft area because the poly mount amplifies the sound.

eZg

iTrader: (5)

maybe exhaust movement?? maybe heat shield?? honestly not even sure there is a stock heat shield....

you have almost covered almost everything else besides suspension.

zakmartin

Year & mileage please. Also, this thread should be in the maintenance forum.

I am Sam

Car is an 08, Nismo trim, 60k miles. I will check the exhaust shields but something tells me that isn't it. My old trans am used to have the heat shields for the cats rattle around and hit things so I know what that sounds like.

dboyzalter

iTrader: (3)

If your strut bar isnt adjusted correctly it could be hitting the engine and make horrible noises... Dont ask me how I know...

I am Sam

Only problem is that it doesn't do it if I go over speed bumps, even if I roll over them kind of fast to get the car to jump a bit, I won't hear the sound. It seems to be tied to the transmission/drive shaft because it will only happen in gear.

ojai33

I had similar issue. Thought it was driveshaft. Met a Ace Mechanic that worked at Nissan Dealer.
He heard the noise, said it was the rear axle splines needing grease.
I was not convinced but after he worked on the car the noise was gone!
He said axle splines were rusty.

I am Sam

Update, I got the car on the lift again today. Still can't seem to find anything that would be the source of my noises. However I'm now thinking the noise might just be gear backlash from the transmission/diff on account of me having poly mounts all throughout the car and an aftermarket drive shaft. I have a subtle clunk/click when I ease on/off the throttle which sounds like the gears engaging and disengaging. Then if I blip the throttle quickly (this only works at low rpm) I hear the tapping several times as the revs bounce up and down. I'm starting to think it's mostly normal. I'll just try to avoid driving the car sporadically and see if the noise ever gets any worse. Funny thing is, the car drives perfect under hard accelerating and shifting. It just hates to lug around at low rpm and you hear a lot of noise from the drive-train.