Loud noise after quick shift!!

djs94gt · Dec 23, 2006

So, I finally have 700 babied miles on my new 2007 GT and decide to wind it up to 6000 rpm and do a quick shift into second (Not a speed shift or flat shift, but fast enough to break the tires loose going into second). It goes into second just fine, but when I let the clutch out and got back on the power, I hear a very loud metal noise, almost like a loud crack in the back or under the car. But, nothing changed on the car. It made me nervous, but I tried it twice again, with no problem whatsoever. Does anyone have any ideas on this?? Maybe something got hurt or something snapped into place.

manystangs · Dec 23, 2006

If it feels ok. maybe the spare tire is loose or possibly loose exhaust somewhere.

metroplex · Dec 24, 2006

It's drivetrain slop. I can hear it doing 1500-2000 RPM 1st to 2nd gear upshifts if I let off the clutch too fast.

stang8urimport · Dec 24, 2006

Yep. Mine does it also. It's so damn annoying. You have to be super smooth with the clutch, or the rear end makes all kinds of clunking noises. My got worse with the BMR lowers. The poly's transfer all that noise that the factory bushings help drowned out. When I bring mine in for it's first oil change, I'm going to mention the clunking and axle whine.

xbone · Dec 25, 2006

Seems like the 5 speeds are having problems, wonder if its because that trans is Hecho En Mexico?

metroplex · Dec 25, 2006

If you release the clutch just ever so gently at the right point, you won't hear the clunk.

metroplex · Dec 25, 2006

BTW

If I'm in gear and cruising at 1500-2500 RPM, i can make the clunking noise appear when applying throttle. My 2000 Crown Vic does the SAME thing and both cars have 3.55s (Ford 8.8" rear end).

I'm wondering if the 3.55 gear set is spaced in a way that makes it easy to hear the clunking noise? I've never heard it on other vehicles and people have been telling me it is because of driveline slop. The Crown Vic has a 1-piece steel driveshaft while the GT has a 2-piece steel driveshaft (different designs). Both vehicles exhibited this clunking noise with less than 10 miles on the odometer (basically direct from the factory). Both vehicles have 3.55:1 rear axle ratios. I confirmed my Vic's backlash was in-spec and axle bearings looked GOOD.

I'm not too worried with the Vic because I've taken the rear end apart several times (differential carrier swaps) and never noticed anything abnormal. With the GT, the sound definitely comes from the rear-end. I have not heard any driveline howl/vibration or groaning during low speed turns with the GT though.

stang8urimport · Dec 25, 2006

metroplex said:
If you release the clutch just ever so gently at the right point, you won't hear the clunk.

Understood, but it shouldn't happen. My 90 5.0 has spherical axle bushings, all the control arms have rod ends on them, or metal sleeves.. no poly/rubber in the suspension... And I hear NO axle whine with 107,000 miles on the stock rear end, nor any clunking. It's not normal, and you shouldn't have to tailor your driving around a NEW 28,000 dollar cars' needs so it doesn't clunk. That's what erks me.

Marine One · Dec 25, 2006

xbone said:
Seems like the 5 speeds are having problems, wonder if its because that trans is Hecho En Mexico?

So much for all the "Buy American" hype.....

metroplex · Dec 25, 2006

PoopDawg said:
Understood, but it shouldn't happen. My 90 5.0 has spherical axle bushings, all the control arms have rod ends on them, or metal sleeves.. no poly/rubber in the suspension... And I hear NO axle whine with 107,000 miles on the stock rear end, nor any clunking. It's not normal, and you shouldn't have to tailor your driving around a NEW 28,000 dollar cars' needs so it doesn't clunk. That's what erks me.

How are you releasing the clutch during each shift? Are you just dumping it? For normal driving, if I rapidly let off the clutch for each shift, it'll be a bit jerky and I'll hear the clunk. If I'm cruising and suddenly "jolt" the driveline, I'll also hear a clunk. I do not hear any axle whine or rear end groaning that others have experience. This is the same clunk I hear in my 2000 Vic (8.8" w/ factory 3.55s) which has the same rear-end as the GT. The only differences are that the GT has 31 spline axles and possibly the carbon fiber clutches but neither should have an impact on the clunk.

stang8urimport · Dec 25, 2006

I shift normally. I don't go around shifting like speed racer when I'm driving around town. All I've ever owned are sticks, and I've cut 1.50 short times with my old Mustang. It's not the driver.

metroplex · Dec 25, 2006

PoopDawg said:
I shift normally. I don't go around shifting like speed racer when I'm driving around town. All I've ever owned are sticks, and I've cut 1.50 short times with my old Mustang. It's not the driver.

I wasn't asking about how you shift. I inquired about how you released the clutch. Most drivers with decades of experience with manual transmissions generally cannot explain it since they've gotten so used to it. On the S-197 GT's hydraulic clutch system (older Stangs used cable clutches IIRC), releasing the clutch too quickly while driving normally causes a clunk in the driveline (isolated to the vicinity of the rear axle). I do not think it is a serious problem because I hear it on my 2000 Vic with the 4R70W (automatic transmission) and the factory 3.55s. This is not a gear whine, axle howl, or anything like that. It's a simple CLUNK in the driveline. Releasing the clutch a few ms slower at the friction point eliminates this clunk.

Also, speed racer-style driving is not required to hear this clunk. I can do it with sub-2000 RPM shifts or heck, no shifting at all. I managed to reproduce this clunk while cruising in gear.

stang8urimport · Dec 25, 2006

Listen. My point is no matter what ****ing clutch, no matter how it's engauged, it SHOULDN'T CLUNK. What do you not get about that? Want me to explain how I release the clutch?!?! I slooooowly release the pedal, as if I am working with a fine piece of art. When I get halfway, I can feel the clutch grab as if I am making passionate love to it... Jesus Christ. I drive a stick like I have always drove a stick and it has never ever ever caused any problems, hydraulic or cable actuated.. it doesn't matter! I have a stupid ****ing clunky, whiny, retarded ass rear end in the car I just spent a TON of money on. It PISSES ME OFF.

metroplex · Dec 25, 2006

In case you missed it the first few times, I have the same clunk in my Crown Vic which has an automatic transmission. I can reproduce the clunk in either the Mustang GT or the Crown Vic with the same method. Both vehicles have factory 3.55s and a 8.8" carrier. The GT has 31-spline axles from the factory, and the Vic has 28 spline axles. I believe it has something to do with the 3.55 gear set.

Don't get pissed at me. Visteon or whomever supplied components or assembled the rear ends on the Mustangs.

stang8urimport · Dec 25, 2006

I don't care about your Crown Vic! Why would I or anyone here? If your rear end clutchs, you should have also taken it in for warranty work when you noticed is, as I will be.

metroplex · Dec 25, 2006

PoopDawg said:
I don't care about your Crown Vic! Why would I or anyone here? If your rear end clutchs, you should have also taken it in for warranty work when you noticed is, as I will be.

Because it has the same 3.55 gear set in a Traction-Lok 8.8" carrier; the same as the ones used in S-197 GTs. I was just trying to be helpful and friendly.

When you take in your car for a checkup under warranty, the dealership is going to tell you it is normal even after 2-3 trips back and forth to the dealership. I've torn apart the rear end on the Crown Vic and didn't find anything wrong. It's just the nature of the beast. If you want stuff actually fixed, don't take it back to the dealership unless they know exactly how to fix the problem. That's coming from over 30+ years combined experience dealing with Ford vehicles and the Ford dealership network.

stang8urimport · Dec 25, 2006

metroplex said:
Because it has the same 3.55 gear set in a Traction-Lok 8.8" carrier; the same as the ones used in S-197 GTs. I was just trying to be helpful and friendly.

When you take in your car for a checkup under warranty, the dealership is going to tell you it is normal even after 2-3 trips back and forth to the dealership. I've torn apart the rear end on the Crown Vic and didn't find anything wrong. It's just the nature of the beast. If you want stuff actually fixed, don't take it back to the dealership unless they know exactly how to fix the problem. That's coming from over 30+ years combined experience dealing with Ford vehicles and the Ford dealership network.

I've also worked for Ford as a tech, and know that when the S197's came out, the dealer was replacing every piece in the rear end to make it stop. It's a factory fault, and incorrectly set up gears.

djs94gt · Dec 26, 2006

Thanks for all the input. I've been driving sticks for a long time, so I am aware of various noises from the rear end when driving around. I just never heard such a loud cracking noise when I shifted under the conditions I originally described in the first post. I was concerned something didn't break, loosen or weaken. Are the drivelines on these cars fairly reliable? I never had any trouble or heard this kind of noise on my last car, a 94GT with a Vortech. or my 88GT before that.

metroplex · Dec 26, 2006

The one thing I did not check on the Vic's rear end was the pinion depth or preload.
The backlash was in-spec and reducing that had no effect on the driveline clunk.

The reason I even mentioned the Vic was because it is the same type of clunk as the one in the S-197 GT with the manual transmission. It was harder to find the source of the clunk in the Vic, but the GT is a much smaller car and the clunk is definitely 110% coming from the rear end.

Fourth Horseman · Dec 26, 2006

I've been assuming the noise was from the u-joints in the two-piece drive line. But if you guys are right and it's coming from the rear end I'd be interested to hear if anybody who had the noise and switched to lower ratio gears after-market still has the noise.

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