# Lower-Speed Downshift Clunk



## MP81 (Jul 20, 2015)

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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## MP81 (Jul 20, 2015)

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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## MP81 (Jul 20, 2015)




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## MRO1791 (Sep 2, 2016)

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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## MRO1791 (Sep 2, 2016)

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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## MP81 (Jul 20, 2015)

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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## mike_D (Dec 16, 2019)

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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## MP81 (Jul 20, 2015)

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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## BDCCruze (Jul 12, 2017)

My 6->5 downshift is hard if the fluid is cold. Pretty much goes away when warmed up.


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## MP81 (Jul 20, 2015)

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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## MP81 (Jul 20, 2015)

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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## MP81 (Jul 20, 2015)

So just to update this, as I'm not sure if I had made these observations before, or if this is newer behavior:

We park the car in the driveway, and obviously back it out onto the street to get going somewhere. When you shift from park to drive, it does the click/clunk noise. Then, as you are backing up onto the street, slowing down for the gear change to drive, it'll make the noise again, just before you stop. Then it makes the noise again when you shift into drive.

It seems like it's gotten louder, but that may very well be from it being warmer out now and me having the windows down.


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## Diesel4Ever (May 30, 2018)

Are you sure there isn’t a broken mount causing the noise?


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## MP81 (Jul 20, 2015)

Last time I was under the car (few months ago) I didn't see anything, but that's a good thought. I'm not even really sure what the transmission mounting scheme is on these things...


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## MP81 (Jul 20, 2015)

I took a peek at the mounts, and they all seemed to be good (from what I could see from the engine bay - which isn't much - at least).

However, today, since my wife was leaving, I popped the hood, and had her shift back and forth between Drive and Reverse with her foot on the brake, so I could listen for the sound and see if maybe I could spot a source.

Well, I can certainly say it isn't coming from the engine bay. Where does it seem to be the most "sharp"/loud? The center of the **** wheel. And out _by_ the wheel. Definitely does not seem further inboard, closer to the transmission. So the transmission may not be the culprit, it's just tied to certain shifts (Park to Drive, Drive to Reverse, Park to Reverse, nearing a stop, and any time you get on and off the gas in 4th gear).

When the vehicle completes its shift, and you see the car's weight shift a bit from said shift (working against the brakes), that's when it pops/snaps.


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## Shroomie (Jan 16, 2017)

MP81 said:


> I took a peek at the mounts, and they all seemed to be good (from what I could see from the engine bay - which isn't much - at least).
> 
> However, today, since my wife was leaving, I popped the hood, and had her shift back and forth between Drive and Reverse with her foot on the brake, so I could listen for the sound and see if maybe I could spot a source.
> 
> ...


How do your rotors look? Last time you messed with the brakes?


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## MP81 (Jul 20, 2015)

Did pads and rotors back in mid-October, so they're nice and fresh.


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## revjpeterson (Oct 2, 2013)

MP81 said:


> I took a peek at the mounts, and they all seemed to be good (from what I could see from the engine bay - which isn't much - at least).
> 
> However, today, since my wife was leaving, I popped the hood, and had her shift back and forth between Drive and Reverse with her foot on the brake, so I could listen for the sound and see if maybe I could spot a source.
> 
> ...


I'd take a real close look at the CV joints if you haven't done that yet.


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## plano-doug (Jul 1, 2015)

MP81 said:


> Where does it seem to be the most "sharp"/loud? The center of the **** wheel. And out _by_ the wheel.


I've learned, on the Impalas, the fix for this is to lube the splines on the axle where it goes thru the hub. A good amount. 

The necessary amount for lubrication isn't great, but to deaden the clunk, put as much on as you can without it oozing all over your driveway 

Doug

.


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## -loki- (Dec 13, 2019)

Check your a arms, wheel bearing.

Get that wheel off the ground and see if can duplicate the sound by applying force in different directions with a 2x4 (be careful not to damage the car)


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## MP81 (Jul 20, 2015)

I'll be having her turn the wheel all the way to the right and doing the same "test" so that I can get a good look and see what's going on - grabbing the axle should tell me pretty quickly if it is the culprit, or if it's in the hub/wheel bearing - or if it's something else. 

I meant to do it today, but I spent 7 hours out in the sun, in high-80s, in my driveway finishing up my brother's Mustang (which has basically kept me busy for a **** month now), so I wasn't about to do anything else, haha.


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## pandrad61 (Jul 8, 2015)

Mine has a slight click when coasting down speeds in auto. It’s barely auditable and honestly don’t notice it.


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## MP81 (Jul 20, 2015)

After we had finished up with the Mustang and took it for a test drive, my brother and moved cars around and took a look specifically at the axle with the wheel cranked all the way to the left - when it makes that click you can see the whole axle rotate forward or backwards (depending on what gear you shifted into) - something it _should not_ be doing with the brakes held. We confirmed that by looking at the right front's axle - no rotation at all (just the typical raising or lowering due to being loaded against the brakes). 

I was worried that maybe the caliper was loose or something from when I did brakes (even though I know for a fact I torqued those bigass bolts to spec), but they're not - plus, we'd experience plenty of noise elsewhere if that was the case.

So I am leaning towards slop between the axle splines and the splines in the hub, based on what we're seeing.


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## pandrad61 (Jul 8, 2015)

MP81 said:


> After we had finished up with the Mustang and took it for a test drive, my brother and moved cars around and took a look specifically at the axle with the wheel cranked all the way to the left - when it makes that click you can see the whole axle rotate forward or backwards (depending on what gear you shifted into) - something it _should not_ be doing with the brakes held. We confirmed that by looking at the right front's axle - no rotation at all (just the typical raising or lowering due to being loaded against the brakes).
> 
> I was worried that maybe the caliper was loose or something from when I did brakes (even though I know for a fact I torqued those bigass bolts to spec), but they're not - plus, we'd experience plenty of noise elsewhere if that was the case.
> 
> So I am leaning towards slop between the axle splines and the splines in the hub, based on what we're seeing.


Let’s hope it’s the axle stub that’s got play and not the female end into the transmission. If both of them have excessive play could be expensive.


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## 16Cruze84 (Nov 27, 2018)

MP81 said:


> [/QUOTE


Mine is doing something similar. Mine is a 6-speed and between 1st and 2nd and 2nd and 3rd both upshifting and downshifting it will make kind of a ratchet and clank sound. I thought it might be the linkage assembly but I wanted some opinions before I go spend money to have it checked out.


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## MP81 (Jul 20, 2015)

pandrad61 said:


> Let’s hope it’s the axle stub that’s got play and not the female end into the transmission. If both of them have excessive play could be expensive.


Based on where the sound seems to be, it would be out on the wheel hub side.

With the wheel turned, you could pinpoint the cross-car center line to be right near the wheel.


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## plano-doug (Jul 1, 2015)

I saw this on FB, and this thread immediately came to mind 

Doug










.


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## MP81 (Jul 20, 2015)

I just saw that one too!

Hopefully I can get it on the first try...


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## Gecks (Jul 31, 2020)

MP81 said:


> I just saw that one too!
> 
> Hopefully I can get it on the first try...


Gday mate, did you sort this out? Ive had exactly the same problem. Thought it was transmission but after replacement is still exactly the same. My CVs seem good and bushes etc all sweet so Im really keen to see if you solve this. Others seem to have had the issue also.
Cheers,
Josh


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## MP81 (Jul 20, 2015)

Not yet - but it's still making the noise. Potentially louder than before, but we also don't drive the car (or any of our cars) a lot at the moment, so it's hard to actually compare it.

The big question, once I finally dive into it, is: are the splines on the axle the issue, or the ones in the hub?


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## Gecks (Jul 31, 2020)

MP81 said:


> The big question, once I finally dive into it, is: are the splines on the axle the issue, or the ones in the hub?


Good question. I am yet to watch for axle movement while braked and changing from drive to reverse to see if I can reproduce what your seeing. I removed the battery and box tonight to double check the transmission mount was good and tight and seemingly no issues so back to the axle.
Cheers,
Josh


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## Gecks (Jul 31, 2020)

Well, I didn't manage to reproduce seeing the axle move. I did find the rear engine mount was moving a lot however. Changed today wondering if it could be the problem. No dice, clunk prevails. 
Cheers,
Josh


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## Shroomie (Jan 16, 2017)

MP81 said:


> Not yet - but it's still making the noise. Potentially louder than before, but we also don't drive the car (or any of our cars) a lot at the moment, so it's hard to actually compare it.
> 
> The big question, once I finally dive into it, is: are the splines on the axle the issue, or the ones in the hub?


I'm willing to bet it's wear on the axle spline, you will see some wear on the teeth.. guess it could be the hub also. Probably both as time goes on and it gets worse


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## MP81 (Jul 20, 2015)

Still dealing with this - had a thought based on another post I had seen where the axle nut was loose, since it'd be easy to check. My torque wrench only goes up to 150 ft.lbs, and I can twist it up to 160 ft.lbs. So unless it's just not torqued to 185 ft. lbs, I don't think the nut torque is the issue, since I'd expect it to be loose at 160 ft.lbs.

Oh well, was worth a shot.

Now that I've got the rear brakes done, the EGR and throttle plate cleaned, maybe I can take a look into this a bit more now. It's just not that easy to pinpoint exactly what component is causing the issue. Would rather not try and guess.


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## Gecks (Jul 31, 2020)

Well at least you eliminated something. Im still looking as well. I can reproduce the clunk by engaging drive then reverse then drive etc with foot firmly on the brake and loading the engine. It will clunk back and forth.
I dont want to be just throwing money at the car to achieve nothing. 
Mines at the mechanics for service today and we are supposed to be taking another drive to show him the sound. See what happens...


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## -loki- (Dec 13, 2019)

Have engine mounts been checked, sounds like the poly is out of one.


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## MP81 (Jul 20, 2015)

Gecks said:


> Well at least you eliminated something. Im still looking as well. I can reproduce the clunk by engaging drive then reverse then drive etc with foot firmly on the brake and loading the engine. It will clunk back and forth.
> I dont want to be just throwing money at the car to achieve nothing.
> Mines at the mechanics for service today and we are supposed to be taking another drive to show him the sound. See what happens...


Yup, mine's exactly the same. If the converter is locked, and you go on and off the throttle it'll click each time - or changing gears to one where the converter locks.

Curious as to what it turns out to be...if they figure it out, instead of saying "cannot replicate".



-loki- said:


> Have engine mounts been checked, sounds like the poly is out of one.


Haven't dove too deeply into those, but with the wheel turned, you can see a "mismatch" between movement in the axle and in the wheel when you switch between gears with your foot on the brake, and the sound definitely comes from "within" the wheel hub.


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## Gecks (Jul 31, 2020)

Well, no more insight from my end. After the service then rebooking to replace leaking water pump then cracked thermostat housing, leaking cam sensor seals, filter housing seal and turbo oil pipe the mechanics had another decent going over the car and can reproduce the sound and they admit it's there. However they can not pin point the issue. 
Everything seems tight with little play to be found. Remaining engine mounts are seemingly are ok. Their gut feeling was it was still in the transmission however while not impossible surely the persistance of the problem with the 3 separate transmissions the car has had makes it improbable thats the culprit. 

Back to mounts though I suppose brakes applied, selecting gears and seeing the driveshaft move as you did could be the engine moving foward and backwards in the mount..... or still perhaps a spline issue.


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## MP81 (Jul 20, 2015)

I have a feeling it is related to this: https://static.nhtsa.gov/odi/tsbs/2019/MC-10168212-9999.pdf

If it's not going to cause any issues, then I won't bother dealing with pulling the hub and/or axle.


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## wikiriki (Dec 11, 2013)

MP81 said:


> 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?


Mine has an occasional very hard downshift during similar conditions to what you describe. I can't duplicate it on demand, so just chalked it up to some qwerky intermittent gremlins.


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## Gecks (Jul 31, 2020)

MP81 said:


> I have a feeling it is related to this: https://static.nhtsa.gov/odi/tsbs/2019/MC-10168212-9999.pdf
> 
> If it's not going to cause any issues, then I won't bother dealing with pulling the hub and/or axle.


Thanks for sharing this. Sounds like this is the problem, a shame not sensibly fixed but atleast you can live with the knowledge nothings about to fall off. 
Cheers,
Josh


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## MP81 (Jul 20, 2015)

Yup - I actually started hearing something similar on my Cobalt - though not nearly as loud - so it seems somewhat common. I guess it does make sense.

The grease suggestion earlier in the thread might be a good idea to quiet it down, provided I can get the axle out without removing the wheel hub (on the Cruze - I know I can with the Cobalt).


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