Hi all,
I experiencing a strange noise on my manual 07 V8 Vantage with 23k miles. I have searched like crazy but cannot find anyone who experienced this issue.
When I am coasting in gear I get a noticeable constant but random clunking/rumbling noise from the back of the car. Whats strange is if i push in the clutch while costing but leave it in gear the noise continues even with the engine RPMs at idle, however if I pull it out of gear the noise immediately stops. I do not have to let out the clutch for the noise to stop, just pulling it out of gear while coasting will make it go away regardless of clutch position. If I push it back into any gear the noise comes back. it gets worse when the car is fully warmed up after a long drive. I recently did a transmission fluid change (the noise was occurring prior to this) to check for any metal debris in the gear oil in case it was a bearing in the transmission but did not find any metal material on the magnetic drain plug.
My best guess is something related to the prop-shaft support bearing or possibly something related to the input shaft of the transmission. From what I understand since the wheels are moving if a gear is selected this would cause the prop-shaft to spin regardless of whether the clutch is depressed or not, only while in neutral on the gear stick would the transmission be truly be disengaged from the wheels.
I am hoping its not something internal in the transmission. It shifts very smooth and no noises under hard acceleration, only while coasting without load. if the car is stationary there is no noise.
Welcome any input or idea and hoping someone can chime in who experienced this.
Thanks.

 

If I were you, I'd want to get a look at that torque tube and give it a good shaking to see if its the universal joint versus something like a throw-out bearing or shaft bearing internal to that transmission. I think the shaft should keep spinning when you depress the clutch to disengage the transmission from the engine because it is fixed to the trans axle at the rear, but decouples at the engine end (clutch). In neutral I think it would be fully decoupled from spinning at the transmission end and clutch end since there's no gear engagement.

I.E. wouldn't the rear axle being fixed via the transmission would keep the shaft spinning while the car is in motion in gear whether the clutch is in or out?

I would guess you have a good lead with the shaft bearing, or a universal joint, but in any case I'd get it on a lift and start looking.

 

Appreciate the response and reaffirming my theory. I am fortunate enough to have a lift at my house and have given the area a good inspection already, but obviously haven't had anything apart yet. I wanted to make sure what I was thinking made sense before i go to the effort of pulling the trans-axle to check the torque tube since I assume it will be a fairly big job. Too bad I don't need a clutch, (i'm probably the first Vantage owner to say that) this would be the perfect time for it.

 

You mean propeller shaft not torque tube. You can’t access the shaft so you can’t examine u joints as suggested above.

 

My mistake, I was using torque tube as synonymous with prop-shaft. what i meant is I'm thinking it could be the prop-shaft support bearings housed by the torque tube. I understand there are no traditional U-joints.
I'm under the impression I could get access to the rear portion of the prop-shaft if i removed the trans-axle and be able to check the rear support bearing with it still in the car. This would also allow me to give a general check for play on the trans-axle input shaft. This sound only seems to occur when the trans input shaft is spinning along with the prop-shaft and the car is under no load. That leads me to believe it has to be either prop shaft related or trans-axle. The noise is noticeable enough that if the trans-axle is broken I'd hope it would have been leaving metal debris so fingers crossed it isn't that...

 

The driveshaft (inside the torque tube) is spinning anytime the engine is running, and the clutch pedal is not depressed. This means that the driveshaft will be spinning regardless of the transmission being in gear, or in neutral. The input shaft for the transmission will also be spinning anytime the driveshaft is spinning. Because the noise is present regardless of clutch position and also changes with gear position in the transmission, I would suspect that the issue lies within the transmission somewhere.

 

Does it do it in reverse as well?

 

Great point, the noise does stop completely if I let out the clutch with neutral selected while coasting. which as you said would mean the driveshaft would be spinning (and the input shaft). That eliminates my support bearings theory, which really only leaves the transmission. If it was cv axles I would suspect the noise would be unrelated to being in gear since they are spinning while moving regardless. Dang... well If it's something internal with the trans I will probably just see if it gets worse and maybe start looking for a deal on a used one. This is not just a subtle gear chatter, its enough that I would be embarrassed with a passenger, something is definitely not right.

Have not tried moving fast enough in reverse to see, It really only becomes noticeable if i'm going over 10mph, will try when I have a chance though

 

I'd suggest it's the transmission input shaft. If you have a lift, get it on stands with some in the car, select top gear, run it up to 3k rpm and let it coast down while under it and see if you can pinpoint the noise.