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Discussion Starter #1 (Edited)
This is the best way I can describe it, at least. Seems to be when you're slowing down gradually, it'll be a kind of hollow "clunk" noise, once, just in front of the driver footwell (or so). Then generally it will do it a second time right as you're stopping. This doesn't happen every time, but it certainly was something I heard this morning, while my wife was driving into work, and I have heard it before (I believe prior to the Trifecta tune, though perhaps not).

Of course, when I had my camera recording, it chose not to do it. When we leave work here in a couple hours, I'll try and get a recording of it. Since I'm not driving, I can't see if it truly is when a downshift occurs or not, but I'll try and keep an eye on the tach.

Anyone have something similar to this happening?
 

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Discussion Starter #2
Bit more info from the drive home, in a bit more traffic, and watching the tach (and speedo). The clunk that occurs just as you're coming to a stop happens right around 5 mph and you can watch the tach pop up a tiny bit just as it does that.

The other thing it does that is around 25 mph or so, and we found out it'll do it multiple times if you accelerate, then let off, then get back on the throttle again, all in a short period of time - typical to city traffic (and people who cannot drive). The tach jumps up and down considerably when that happens.

I did get a video, so I will upload that here soon. You can see the tach, the digital speed reading and you can absolutely hear it (a bit louder than in real life, but all the better for diagnosis).
 

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Discussion Starter #3
 

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That seems to be the Torque converter lock-up kicking in and out. Are you running the original fluid, and if so how many miles. It is not really a lifetime fill as the manual might suggest, I would not go more than 50K on that fluid, and if you have not changed it, that is first thing I'd do, as it could make the engage and release of the torque converter lock more harsh just by old, thin and worn out fluid in the transmission.
 

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At one point I had 2 Gen 1 Diesels, the second one I bought used with 45K miles that were put on the car in 10 months by the prior owner. It did something similar to your video and had some odd shift behavior, especially compared to my other much lower miles car with the same power train. I did the fluid replacement per the DIY section, using the Amsoil and it was massively improved. I ended up trading that car for the Gen 2 my wife now has, she never liked the used car, mostly because it had a bit of residual smoker smell to it, but otherwise it was a good car.
 

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Discussion Starter #6
Car is running AMSOIL fluid in there...did that back in January of 2018 (at around 71k miles), and then had to do the trans lines a couple months (and 3000 miles later), so a little bit more AMSOIL into there after that. Roughly around 103-104k miles now.

Oddly enough, ever since then, the trans has not been great. This just seems to be the next thing in that list.

But yes, I was thinking torque converter lock/unlock, since I know this trans like to lock the converter up a good amount more than most autos seem to.
 

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Just read this and even before I read the others reply I was going to suggest changing the transmission oil. MIne does the same thing. If you coast to a stop you will notice it more than braking quickly to stop. One day I decelerated with the transmission in manual mode, it seems the shift from 4 to 3 hits a bit hard. Remember the diesel is a fairly high compression engine. Changing the trans fluid did help but it does not seem as smooth as it was when it was new. Another comforting thing too is that my changed trans fluid did not have any metal in it. Metal in it would have indicated a real problem brewing. In summary this is just the way this transmission downshifts. So get the fluid changed, it will be better, and don't worry too much about it.
 

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Discussion Starter #8
The fluid only has about 30k miles and about two years on it, and it is Amsoil...shouldn't be needing replacement just yet...

I bought some Race Ramps wheel cribs so I can get the car up, but level (without using stands), and get the aeroshield off and make sure those stupid lines aren't leaking again.
 

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Discussion Starter #10
Yeah, this seems to be present cold or warm. It seems to occasionally be louder if it is colder out, so, that's great.

When I do my oil change in the near future, I'll be pulling the belly pan and checking the trans fluid level. It's been a couple years (and 35k miles) since I did it last anyway, so it's worth checking. Moreso to make sure these stupid trans lines aren't leaking again. I have the old ones, which I'd do the $5 mod on and reinstall, though I'd rather not because that process suckkkkks.
 

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Discussion Starter #11
I checked the trans fluid when I did my oil change on Saturday (and added the specified 0.5qt after closing up the check plug), and found there to be no change in this - still does the clunk noise when the TC locks or unlocks. It drives fine, it's just annoying.

Something else is amiss inside the trans, it would appear. Solenoid or something.
 
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