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Thread: Does anyone know what makes that grinding noise on the DCT Reply to Thread
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Topic Review (Newest First)
05-09-2015 06:03 PM
Arco-Zakus
Shift happens

Quote:
Originally Posted by Kabigon View Post
Keep in mind that we are talking about a DCT.
Gears are not being engaged/disengaged during a "gear change".
Rather, it is the clutches that are engaging/disengaging. ...
That's true, but before that shift happens by switching between clutches the TCM has to select the ratios behind the clutches from the 6 (not counting reverse) that are available. That is when the synchronizers get to do their job -- or not. The grinding could be occurring then. Especially if the clutch that is supposed to be disengaged while the shift fork is selecting a new pair of gears is not.

Quote:
Originally Posted by Kabigon View Post
I believe that the noise is directly related to the unloaded clutch disc and that it isn't actually a grinding noise at all.
If so, then why don't the clutches in cars with the MTX-75 manual trans make those kinds of noises when their disk is unloaded?

If you are correct about that source of the noise, it may be in addition to the sound gears grinding, rather than instead of it. People may be hearing different noises in different cars but think they're talking about the same one. The memo from Ford says the noise from a bearing occurs at 2 mph, while owners describe a grinding sound occurring during shifting, which occurs at much higher speeds than 2 mph.
05-09-2015 06:01 PM
Arco-Zakus
Quote:
Originally Posted by supernova1 View Post
... This noise sounds to me like a transmission "teeth biting", and I speculate that it is either caused by incorrect syncro design (or damaged syncro), or gears are being engaged too soon - before syncros have enough time to do their job. In either case "tooth biting" does shorten the transmission life. I hope I am wrong, and somebody has a better theory. ...
Another possibility that seems more likely to me is that one of the gear selectors is being moved (to select a different pair of gears) with the clutch it is associated with not being fully disengaged. Same noise I would get with my manual transmission if I tried to push the lever into any gear with the clutch pedal not pushed all the way in, even if the synchros are working perfectly when the clutch is disengaged.

This could be caused by software logic faults ("bugs"), a defective actuator, or electrical faults (wiring defects, insufficient current capacity due to poor ground connections or current overload, etc.) or some combination. Any of those could cause intermittent or inconsistent symptoms and be affected by temperature variations.


Quote:
Originally Posted by supernova1 View Post
... As for a throw ball bearing as a noise source - I have never seen a ball bearing that makes noise as horrible as I have on my car. If this is truly the case, it is a major design flaw. ...
Same thing I've been thinking since Ford distributed the "PowerShift 6 Speed Operating Characteristics" memo:

Quote:
• Low speed grinding. A slight grinding noise may be heard at about 2 MPH. This noise
is more evident during “trailer-hitching” events (see below). This noise is caused by a
normal bearing rotation and does not affect the durability of the transmission.
05-02-2015 01:31 PM
Kabigon
Quote:
Originally Posted by supernova1 View Post

This noise sounds to me like a transmission "teeth biting", and I speculate that it is either caused by incorrect syncro design (or damaged syncro), or gears are being engaged too soon - before syncros have enough time to do their job. In either case "tooth biting" does shorten the transmission life. I hope I am wrong, and somebody has a better theory.
Keep in mind that we are talking about a DCT.
Gears are not being engaged/disengaged during a "gear change".
Rather, it is the clutches that are engaging/disengaging.

I believe that the noise is directly related to the unloaded clutch disc and that it isn't actually a grinding noise at all.
05-01-2015 06:42 PM
pintoman I heard on a website that maybe "scrubbing" the transmission might help.....haven't tried it yet but maybe this weekend I find a deserted road and give it a try. I have noticed today tho' that it makes a hard shift when I jump on it hard.
05-01-2015 06:24 PM
Arco-Zakus
Quote:
Originally Posted by sailor View Post
Check the thread dates - you're pulling up guesses form 2012 to comment on.
True, but the same comments made back then would be just as valid today. Two and a half years later we still have to guess the answers, lacking any official ones from Ford or Getrag.
05-01-2015 04:45 AM
mr_cassandra
Quote:
Originally Posted by xpartmgr View Post
I know I will likely get flamed for another DCT thread, but I am curious if anyone knows what the noise actually is? I mean Ford says it is normal, many of us have it and it seems totally not normal to us. I was just wondering if Ford has said what or why it makes that noise when it shifts from 1st to 2nd? Why only when it goes from an odd to an even gear? mine does it from 1st to 2nd and from 3rd to 4th, but never from 2nd to 3rd. So I am curious if anyone actually knows what part is making the noise and why it is only some cars but not others? Why only from odd to even gears?

Perhaps this is someplace else, but with all these DCT threads I can't find it! That was a joke.
long story short, most of the symptoms that Ford said were "normal" will go away after a good fix, like revision F.
if they were "normal" how can they go away.
If the dealer gives you the run around, seek out Meagan or the other Ford reps at this board and get your case escalated.
Remember, all your neighbors buy new cars every day, get up in the morning, turn the key and drive away. They don't have to do wide open throttle starts, snorkel deletes, motor mounts and all the other "fixes" people will tell you here.
This is what you should get too.
04-30-2015 03:43 PM
sailor Theories vary with the circumstances when the noise occurs, most common being a result of the clutch engagement "shudder" that seems to occur easily with these.

Many pieces in that assembly which could vibrate, and even with a std. single clutch manual clutch shudder is often described as a grinding noise.

The other circumstance when gear grinding COULD occur is when the trans. needs to shift unexpectedly, such as on & off throttle application. It normally pre-selects the next gear to be engaged, and could have difficulty at times when that choice keeps changing.
04-30-2015 03:24 PM
supernova1
Quote:
Originally Posted by sailor View Post
Check the thread dates - you're pulling up guesses form 2012 to comment on.
So is there a better theory about DCT noise at the moment? I was not able to find it anywhere on the forum.
04-30-2015 03:19 PM
sailor Check the thread dates - you're pulling up guesses form 2012 to comment on.
04-30-2015 03:14 PM
supernova1
Quote:
Originally Posted by StockTalon View Post
The short noise you hear at low speed/quite times is the box grabbing the next gear.
If this is the case, this transmission noise is NOT normal. A good transmission is supposed to have synchronizers on each gear - and DCT transmission does have them (Youtube has a good video on the transmission disassembly: https://www.youtube.com/watch?v=6iCRnAUftvI). It is exactly their duty - to make sure 2 gears grab each other at the same speed (initially they naturally have different speeds) to avoid "teeth biting".

This noise sounds to me like a transmission "teeth biting", and I speculate that it is either caused by incorrect syncro design (or damaged syncro), or gears are being engaged too soon - before syncros have enough time to do their job. In either case "tooth biting" does shorten the transmission life. I hope I am wrong, and somebody has a better theory.

As for a throw ball bearing as a noise source - I have never seen a ball bearing that makes noise as horrible as I have on my car. If this is truly the case, it is a major design flaw. A good example - my Toyota RAV4 exhibited a constant whining noise coming from transmission. Toyota acknowledged this as an issue with final gear honing (!), and replaced the whole transmission (!) under warranty to get rid of this minor (abet annoying) noise.
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