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Manual Trans. Thud when shifting

mustang_guy

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It is NOT the drive two piece drive shaft.
It is a combination of the rear end sub chassis and rear end shifting slightly against the main chassis. That is why the clunk thump is such a low frequency sounding noise.
While standing still, I can depress the clutch and rapidly shift between gears. Each time I enter another gear, THUD! Six gear shifts, six thuds. I am approaching 10,000 miles now I have never become used to it or accepting of it. The problem and aggravating noise persists. I read owners of the 2017 also have the thud and the GT350 cars have it too.

I am pretty sure I am moving away from Ford for my next car. I am very disappointment by the total lack of support from Ford with this problem and their lack of providing a fix for a production wide manual shift Mustang defect.
Its mostly related to the PP diff in the cars. My 17 doesnt have it. I also didnt buy a PP. Ive still yet to read any non pp owners complain. Ive also told you that this isnt an uncommom thing on IRS equipped vehicles. I also dont see any autos complaining about it either. You just want to complain, in my opinion.
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Tony Alonso

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Its mostly related to the PP diff in the cars. My 17 doesnt have it. I also didnt buy a PP. Ive still yet to read any non pp owners complain.
It's been a characteristic of my '15 GT without a performance pack since the first week I got the car back in November, 2014. I am used to driveline slop from the live axle days, so I haven't done anything about it.
 

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It's been a characteristic of my '15 GT without a performance pack since the first week I got the car back in November, 2014. I am used to driveline slop from the live axle days, so I haven't done anything about it.
Interesting! I generally hear of no one having that complaint than the vast majority of PP owners. From what ive seen on inspection on a lift (ex ford master tech here) my buddies PP it was the torsen. Id wager if your trak lok is doing it possibly just needs an adjustment. Have you ever tried taking it in? What gear ratio do you have?
 

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I didnt see many older mustangs thud like some discribe during normal driving unless you no lift shifted or banged it hard enough. Is that what you're reffering to?
 

Tony Alonso

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Interesting! I generally hear of no one having that complaint than the vast majority of PP owners. From what ive seen on inspection on a lift (ex ford master tech here) my buddies PP it was the torsen. Id wager if your trak lok is doing it possibly just needs an adjustment. Have you ever tried taking it in? What gear ratio do you have?
It's the 3.55 gear. I've not taken it in because many of the early posts in this massive thread have centered on cushy bushings in the IRS and the IRS cradle shifting. I really didn't want to get into any diagnosis or purchase aftermarket parts to modify my daily transportation. It only occasionally shows up, or at least I don't notice it as much.
 

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I didnt see many older mustangs thud like some discribe during normal driving unless you no lift shifted or banged it hard enough. Is that what you're reffering to?
I heard noise when shifting hard. I don't do that much these days. :-)
 

Kong76

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Its mostly related to the PP diff in the cars. My 17 doesnt have it. I also didnt buy a PP. Ive still yet to read any non pp owners complain. Ive also told you that this isnt an uncommom thing on IRS equipped vehicles. I also dont see any autos complaining about it either. You just want to complain, in my opinion.
Well I have a base 2016 GT and mine has been doing this from day 1 as well. Noticed you straightened up your attitude when Tony responded. Why do you have to be such a prick? I've seen other threads where you respond the same.

Whats your problem? Napolean complex? No girlfriend? Not big enough? Gotta be something... tell us...
 

Draklia

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I've had the thud since day one on my base '16 too. I am not convinced it's a problem in the fact that it will cause damage.
I thought it was just the backlash in the ring and pinion along with a pretty hefty drive shaft, that and the transmission doesn't really have anything in it to quiet it. But just guessing on that. It is annoying though, but life goes on (hopefully).:)
 

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I've had it since day one. 27k miles and over 2 years later, not concerned at all. I've had several other manual trans cars (all Getrag trannies).
 

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People talk about it being a driveshaft issue, a rear end issue, a transmission issue. And you see some situations of replacing a part and it going away for one guy, but not another. Here's my best guess / theory.

The root cause may be there's some amount of drag across the clutch, even when disengaged. This causes the input shaft of the transmission to spin slightly when in neutral, but being in gear obviously provides enough resistance to stop it. When you're in neutral and move into gear, the inertia of the input shaft transfers to the transmission output. Depending on how much backlash is in all of the downstream components, you'll get a thud of varying degree as that inertia is transferred down the drivetrain and all of that lash is used up, forcing the input shaft to stall. More combined lash means more thudding.

So, if you have low lash in the axle, but a bit in the 2-piece prop shaft, putting in a 1-piece shaft reduces the lash - and the inertial movement - enough to make the thud less noticeable. But if there's also excessive lash in the axle, then you don't make enough reduction in system lash to change how the thud feels. It might be more noticeable off the bat in PP cars because 1) the 3.73:1 gears multiply the axle back lash more than the taller gearsets do, and 2) the Torsen lacks a preload spring, which masks the differential gearing lash in the clutch plate diffs. So, more perceived lash comes from the axle. But you can get it in other axle combinations if the prop shaft or transmission system lash is also high enough. You don't get it in A/T cars because the transmission obviously sidesteps the issue.

I could be completely off base on this, I'm just an axle guy. But this is the only thing I've been able to come up with that addresses all the facts as I understand them. You can chase various aspects of drivetrain back lash and improve the situation, but I'd bet that if the clutch could be set up so the clutch disc more fully disengages the pressure plate, the problem would disappear. At least that's my thinking...
 

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The point is, it's a 2015 MY car... there is no excuse for this. Not one single manual transmission vehicle I've driven or owned prior (Subaru, VW, BMW, Nissan Versa, Toyota Scion, '94 Honda Accord) have done the same. It's pitiful. But... you get used to it.
 

Tony Alonso

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I could be completely off base on this, I'm just an axle guy. But this is the only thing I've been able to come up with that addresses all the facts as I understand them. You can chase various aspects of drivetrain back lash and improve the situation, but I'd bet that if the clutch could be set up so the clutch disc more fully disengages the pressure plate, the problem would disappear. At least that's my thinking...
What do you think about the change in the '18 GT to twin-disc clutch and new dual mass flywheel? Purely for higher torque output?
 

EXP Jawa

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What do you think about the change in the '18 GT to twin-disc clutch and new dual mass flywheel? Purely for higher torque output?
I'd expect that the main reason for doing that is increased torque capacity. I doubt it would be done as a thud improvement. In fact, I'd think that with dual-discs, there is an added level of complexity to getting it set up right. One disc might still drag and the other not.
 

mustang_guy

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Well I have a base 2016 GT and mine has been doing this from day 1 as well. Noticed you straightened up your attitude when Tony responded. Why do you have to be such a prick? I've seen other threads where you respond the same.

Whats your problem? Napolean complex? No girlfriend? Not big enough? Gotta be something... tell us...
My attitude has zero influence based on his presence. Ill say what i want to say regardless. Im a bit too old to fear being banned on a forum. Maybe you should stop adding tone to text. Couldnt care less what your opinion of me is.
The point is, it's a 2015 MY car... there is no excuse for this. Not one single manual transmission vehicle I've driven or owned prior (Subaru, VW, BMW, Nissan Versa, Toyota Scion, '94 Honda Accord) have done the same. It's pitiful. But... you get used to it.
Wrx and sti most definitely thud if shifted hard. Their issue is with their diff bushings.
 

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I've decided to purchase a new 2018 Vette instead of the new 18' Mustang. I am tired of fighting with Ford.
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