2008 Mustang GT Coupe 5th Gear Vibrations, Need Advice
I think I may have mentioned this before when I introduced myself, but I'm near a dead end, so I'm going to go into a bit more detail. Hopefully at least ONE of you gents may have some advice for me.
I special ordered my 2008 Mustang GT, and picked it up early November. When it arrived, I noticed that when I put it in overdrive (manual 5th), the car generated an odd sound/vibration, like when you roll down the rear windows in a 4-door car. It's a booming, low frequency sound, and it does it almost exclusively when you ease back on the throttle slightly and cruise. Also, it almost always occurs in 5th gear only... after some time behind the wheel, I can detect it a bit in 4th, but it's just barely noticeable.
Initially I didn't know if this was normal for the cars or not. Some cars are just noisy, right? And I test drove a 6 cylinder manual, then ordered the 8 cylinder, so I had no previous experience with the 8 cyl. After hearing a few complaints online about road noise and the lack of sound insulation in the S197, I figured my noise may be relatively normal. Also, the car was brand-spankin' new, so I thought I'd give it some time to break in before I ran to the dealer crying wolf.
However, 3000 miles and a lot of experimenting later , I was really beginning to believe there was a problem. As I mentioned earlier, always 5th gear, always between 55-75 mph, and depressing the clutch ceased the noise almost immediately. If it was road noise, it shouldn't change so long as my speed remained the same. If it was exhaust vibration, it should occur at a certain RPM no matter what gear (I would assume?). More and more I have become convinced there is a gremlin in the drive train. I decided I'd better test drive another '08 GT manual just to be sure. I was secretly hoping that it would make as much noise as mine, but alas, it was smooth as silk in 5th gear. Try as I might, I couldn't coax the odd vibration from it. Nuts!
I've always heard you never know what to expect out of a car built on Friday or Monday. My car was in the middle of being assembled when the plant shut down for two weeks. Lucky me!
Now let me tell you what I've done about it thus far. Both the local service manager and a technician have ridden with me, and both acknowledged the booming. They first tried rotating the driveshaft 180' (just in case), but that had no effect (despite the fact they claimed the noise was now gone). They have just recently replaced the driveshaft altogether, including all mounts, joints, and bearings. Still no effect at all on the vibration (and again they claim the noise is gone! )
So my question to you all: where should I go from here? I would assume the next course of action would be to examine the transmission itself. Should I expect them to replace that as well if they can't find the culprit, like they did the drive shaft? Seems to me like the service center would balk at that, especially when they've claimed it's been taken care of twice before... I'm beginning to think they really don't know what they're trying to fix. But I'm not crazy, it's there. My wife hears it, and at times the frequency can be downright uncomfortable.
I'm just really stumped, and annoyed, because I really LOVE everything else about the car. Part of me says not to sweat it, that over time I'll probably be replacing all that stuff anyway, but another part of me is ticked that the most expensive car I've ever owned has to be endured. It's almost enough to make me regret going American this time. My Toyota was flawless for 90k miles.
So, any advice? What should I expect the dealer to agree to? Does anyone have any other ideas about what could be causing the problem?
Have the driveshaft balanced before you do aything else. They can keep throwing new ones at it all day long, but if they are all out of balance a little.......
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I would feel the same way if it were me. As irritating as it would be, it will be figured out and solved. Sqidd is right, I would try the drive shaft balancing first and then move to the next most likely source that a lot modify and that is the rear differential. Look at it positive, an excuse to upgrade once you find the problem. My Mustang is by far better than any other car that I have owned. As far as Toyota goes, my experience was not good, with the Camry for my wife that we bought new and has long been gone. From day one we had problems with the transmission and poor paint quality.
Let us know what happens.
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08 Mustang GT Premium
Candy Apple Red / Manual Transmission / 3.55 Gears
O/R H Pipe / Borla Stingers / BMR adjustable UCA, LCA's, Panhard Bar, Eibach Pro Springs
Also, if you get a new lightweight driveshaft have it balanced before you put it on. There are a couple of driveshaft manufactures out there that are not getting the shafts balanced and sometimes straight.
My aluminum driveshaft needed to be balance and straightened. It wasn't a problem at 80mph and I hardly noticed it, but at 150mph it was about to come out of the car!
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Under Construction. Better, Stronger, Faster than it was before.
No, my vibration is mostly between 55 and, oh, 80 or so, though I can detect hints of it at lower speeds during decel. 73 mph will vibrate your foot numb, and rattle your brain.
Considering I've had 2 brand new shafts (the one that came in it and the newest one) and the problem never changed, I have my doubts it has anything to do with the driveshaft. What are the chances of two brand new shafts having identical problems, especially when no one else is reporting it?
And as I mentioned before, it stops as soon as you depress the clutch. The driveshaft will still be spinning roughly the same speed before it begins to slow down, so the noise shouldn't suddenly disappear like it does... it should wind down slowly, but that's not the case. Likewise with the rear differential gears.
That leads me to think it must be something directly related to the clutch, or maybe something in the tranny. I'm not a transmission expert (okay, I actually know nothing about the internals ) but it still seems strange to me the issue only crops up in 5th, and barely in 4th.
I'm going to take it out today at lunch and see if the 73 mph mark causes the same vibes in 4th gear as it does in 5th. After that, I'll be hauling it back to the dealer. 3rd time had better be the charm... I sure as hell don't want to send this thing back to Ford as a lemon, but I will if I have to.
That's got to be killing you. I just got my '07 this weekend, and I'm already worried about sounds and rattles, but I haven't experienced your pain, and I hope I don't. So, are you protected by the lemon law and can get another vehicle?
Your belief it may be in the clutch is plausible. Vibrations like you describe may be due to the load on the drivetrain, and may show up at the same rpm in a different gear. Note the rpms when the vibration starts, then try running steady at the same rpm in 3rd. Maybe it's an imbalance in the transmission gears?!?
That's got to be killing you. I just got my '07 this weekend, and I'm already worried about sounds and rattles, but I haven't experienced your pain, and I hope I don't. So, are you protected by the lemon law and can get another vehicle?
Your belief it may be in the clutch is plausible. Vibrations like you describe may be due to the load on the drivetrain, and may show up at the same rpm in a different gear. Note the rpms when the vibration starts, then try running steady at the same rpm in 3rd. Maybe it's an imbalance in the transmission gears?!?
Yeah, it's driving me nuts. So far the service center has been very friendly cooperative... no coppin' an attitude and telling me I'm imagining things.
About the RPMs. Strangely enough, RPMs have no effect on the noise. It's exclusively speed-dependent. I can run 75 in 5th gear and have huge vibration, and run 75 in 4th with nearly identical vibration. Obviously the RPMs are nothing alike there.
I actually just got back from the service center, and gave them a heads up that all is still not well in Mustangland. I'm dropping it by again tonight, and I've compiled a list of things I've noticed about the nature of the vibration to leave with the keys. Hopefully that will help them diagnose it a little better. It's gotta' be hard to figure this stuff out, considering how little they actually drive it. The guy behind the counter (assistant service manager, I think?) said they'd probably have to call in their regional super-tech-guy-thingie for a look.
BTW, here's my list, should anyone be interested.
Mustang GT (Vista Blue) Problem Review
Vibration/noise can be describes as low frequency "booming" or "humming", similar to the effect of rolling down the rear windows only in a 4 door car. It can be felt as well as heard.
Random vibration/noise occurs between 50-75 mph while "floating" accelerator, or on full deceleration.
Steady vibration/noise also occurs at 73-75 mph in 5th gear and 4th gear (4th not as noticeable). During this time, the vibration can be felt stongly through the gas pedal, and is easily heard.
Noise is speed-dependent. RPM has little effect.
Noise seems to be present only in 4th and 5th gears. Most noticeable in 5th gear.
Depressing the clutch ceases the noise/vibration almost instantly. Releasing the clutch causes the noise to return.
My bet is the rear end is the culprit. Since you've had 2 drive shafts with no change, the diff is about the only speed dependant piece left. Many will make noises/vibration only under power-on and others power-off (I think power-on is more common though).
Once this gets sorted out you will love the new ride. Hang in there!
My bet is the rear end is the culprit. Since you've had 2 drive shafts with no change, the diff is about the only speed dependant piece left. Many will make noises/vibration only under power-on and others power-off (I think power-on is more common though).
Once this gets sorted out you will love the new ride. Hang in there!
That would be my guess as well. There have been a few cases of bum 8.8" housings getting into the production line.
Considering I've had 2 brand new shafts (the one that came in it and the newest one) and the problem never changed, I have my doubts it has anything to do with the driveshaft.
~HA
It could also be said that since the first shaft was bad, and the second one comes from the same place the first one did that the second one could be bad also. Finding solutions happens when you remove variables. You have not removed the variable that would be most likely to cause the problems you are having.
If you don't check the driveshaft for balance and trueness you are a moron. We are talking about $40 here.
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Under Construction. Better, Stronger, Faster than it was before.
It could also be said that since the first shaft was bad, and the second one comes from the same place the first one did that the second one could be bad also. Finding solutions happens when you remove variables. You have not removed the variable that would be most likely to cause the problems you are having.
If you don't check the driveshaft for balance and trueness you are a moron. We are talking about $40 here.
Considering it's a warranty issue, that's the dealership's problem. If they wanna' check for balance, that's fine. If they'd rather replace it altogether, that's fine. However they wanna' spend the $$$, it's no dough outta' my pocket.
What you're talking about would be a full blown manufacturing issue in the drive shaft. What are the chances of two drive shafts both having identical errors arriving at the same location 2 months apart? If it were that widespread of a problem, every '08 out there would be at risk. I haven't seen any other reports like this across 3 forums. I'm not saying it's impossible, it just seems like a longshot, especially considering how many other spinning hunks of metal have yet to be examined.
2008 Mustang GT Coupe 5th Gear Vibrations, Need Advice 
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) but it still seems strange to me the issue only crops up in 5th, and barely in 4th.
