graymetalicsilv

base 2008 350Z stock, 6-speed.

Does anyone have any idea what is going on!!!

When ever the car change suddenly from engine-pushing-wheel to engine-slowing-wheel (such as when you step heavy on the gas while in low gear, then suddenly take your foot off the gas pedal while still in low gear) there is a single "clunk" sound from what seems like the differential area.

Also, from a stop, when ever the clutch pedal is released half way I hear a "clunk" sound from the rear. All this with little or no gas, and me holding the clutch pedal still. It feels like the clutch makes an initial grab, then slips. And if you want the car to move, you have to release the clutch pedal further and give more gas. The idle rpm dips a little at the same time as the "clunk."

I can drive without the "clunk" if I release the clutch pedal unnaturally slow, but I would be holding up traffic. It does not affect drivability, it is just extremely annoying.

Too much free-play in the drive train???

Bad bushings???

Gremlins???

FIXED!!!
Too much free-play in differential (spider gears perhaps?). Replaced the pumpkin with a VLSD pumpkin from an 07 automatic. Still slight clunk, probably from free-play in the transmission. Also, the automatic diff final gear ratio is 3.3 (I think) as opposed to the manual diff of 3.5. This reduced acceleration slightly, but now the computer says I get 28-29 mpg on the freeway.

Deteria

iTrader: (2)

Mine does it too. Same with my cousin's 03 with CD009 transmission. Maybe it's normal.

TreeFiddyGee

Yeah I would say its too much free play in the gear set. Lift the back end of your car and turn your wheel to see how much it spins while in gear. If the gap seems normal, then I'm not sure what else it could be. Also the clunking sound could be the gear set itself hitting back and forth as you let off the gas quickly or go from a complete stop.


BUT, if the sound is coming from the REAR of the car, then that's strange O.o

TheVengefulCo

My friend has this exact same problem on his 323i.. he took it to the BMW dealer and it turned out to be his rear differential mounts. You may want to get this checked out, his diff was offcentered it was bad.

TheVengefulCo

and no if it was your gears then it would be a grinding sounds and usually would be a synchronizer going out. Im almost a hundred percent sure its your differential mounts. Can you describe the problem more to me? it could also be your rear axle, whatever it is do not drive your car hard! my friends 323i has the bad mounts in the front too and one actually broke off last week and bent his front axle so we replaced that. Ill try to upload some pics of the damage!

RMichael

it's normal.

TreeFiddyGee

why would there be grinding sounds? Im saying that first gear is still engaging, but the gaps between the teeth are slightly bigger causing a noticable jerk if u let out the clutch fast. idk. right now its just a guessing game since i have not heard the noise before.

TheVengefulCo

ehh because when gears slam hard together like that, its going to be more than clunk. also, gears are pretty tightly packed into the gearbox so there isnt a whole lot of play but who knows maybe youre right. I think the OP should take a look at the mounts though, ive never heard of a clunk coming from the differential being "normal". Its pretty easy, just jack up the car and remove the plastic protector and youll see them fine. but yeah, i doubt its the gears if its from the rear lol

TreeFiddyGee

Yeah I'm pretty sure im completely wrong

10-E-C-350Z

iTrader: (9)

I had this same problem with a 280z I once owned. My pinion had a bunch of backlash. while cruising I never heard a thing. Then whenever I mashed the gas or shifted with a purpose it would clunk.

winchman

That's definitely not normal.

It's not the gears themselves, either. All modern automobile transmissions are "constant mesh", so all the shifting is done by engaging and disengaging the blocking rings and synchronizers. The parts that mesh when shifting are finer than the gears themselves, so there's not much room for play.

I'd be looking at the clutch master and slave cylinders, especially the slave. It's probably not moving smoothly as you let the clutch pedal out, and that causes it to grab when it does move.

The differential gears normally have only a few thousandths free play or backlash, and they won't make any sound when the load direction changes. If the backlash is more than that, the gears and/or bearings are probably shot.

It could also be a bad universal joint or CV joint. There are six of them to choose from.

Mike1082

I have the same issue. It is outlined in a technical service bulletin.

Do a search for "TSB 04-065 - Suspension Clicking Noise From Rear Axle" on Google, and you will likely find your answer.

TheVengefulCo

thats a different issue altogether lol thats from the loosening of a component of the rear axle. My old G had it, but the clunking is a different thing.

graymetalicsilv

FIXED!! refer to bottom of original post for answer.

TreeFiddyGee

HAHA! what did i tell ya (;