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Discussion Starter #1
Good day to you all ;)

My wife's Q5 TDI developed an interesting problem. Yes, I realize it is not Touareg but this is likely the forum with the most technically saavy folks, so trying out for ideas of what can be wrong / what to check.

In the morning, after the night in the garage, when pulling out of the driveway, I noticed (she reported it, and I confirmed it) that switching from reverse to drive and pressing the accelerator, the car jerks and there is a visible thud, not too loud, but it seems like something engages rather heavily. The car is shy of 48k mile marker, so I'd hope this is not transmission giving up on us. No error codes on VCDS, the car was scanned multiple times. The problem does not go away when the engine is warm, it is just less noticeable. I also noticed it is more visible when going uphil, as if something had problems engaging into drive. No issues I can see in between gears when already in drive.

The second issue is even more bizarre. In the morning, when driving out of the community we live in, and pulling up at the stop sign, I press the brake to stop the car and it seems like transmission is fighting me to the point where I get into panic mode since it feels like brakes are not there. I have to press the brakes deeper to make the car stop. The engine downshifts correctly but it seems like the transmission does not disengage correctly and keeps on pulling the car despite me pressing the brake. This problem seems to disappear as the engine / transmission warms up, but seems to be back when leaving work in the afternoon and going home. Again, the car was scanned many times and no error codes of any sort.

It seems like it is the start of some transmission problems, and while the whole thud thing is not bothersome, the brake problem is more and more concerning. I check the brake pads, rotors, discs, and all looks fine. Brakes engage correctly as far as I can tell, but it seems like the car is fighting me when braking cold.

Thanks for any thoughts / hints. I hope this is not the start of a terror story similar to what I was running into with my Touareg a while back.

On the flip side, the gas Q5 is running just fine, with no issues. I seem to have bad luck with anything diesel-powered.
 

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I guess the thing to look at is what is the engine RPM when this occurs.
I know if I don't wait until my engine RPM settles down to ~650-700 when cold I get the same braking effect initially.
Could be possible the engine isn't going to it's low idle setpoint correctly or in time.
Being you didn't mention it, I'm guessing you have no CEL on?
 

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Good day to you all ;)

My wife's Q5 TDI developed an interesting problem. Yes, I realize it is not Touareg but this is likely the forum with the most technically saavy folks, so trying out for ideas of what can be wrong / what to check.

In the morning, after the night in the garage, when pulling out of the driveway, I noticed (she reported it, and I confirmed it) that switching from reverse to drive and pressing the accelerator, the car jerks and there is a visible thud, not too loud, but it seems like something engages rather heavily. The car is shy of 48k mile marker, so I'd hope this is not transmission giving up on us. No error codes on VCDS, the car was scanned multiple times. The problem does not go away when the engine is warm, it is just less noticeable. I also noticed it is more visible when going uphil, as if something had problems engaging into drive. No issues I can see in between gears when already in drive.

The second issue is even more bizarre. In the morning, when driving out of the community we live in, and pulling up at the stop sign, I press the brake to stop the car and it seems like transmission is fighting me to the point where I get into panic mode since it feels like brakes are not there. I have to press the brakes deeper to make the car stop. The engine downshifts correctly but it seems like the transmission does not disengage correctly and keeps on pulling the car despite me pressing the brake. This problem seems to disappear as the engine / transmission warms up, but seems to be back when leaving work in the afternoon and going home. Again, the car was scanned many times and no error codes of any sort.

It seems like it is the start of some transmission problems, and while the whole thud thing is not bothersome, the brake problem is more and more concerning. I check the brake pads, rotors, discs, and all looks fine. Brakes engage correctly as far as I can tell, but it seems like the car is fighting me when braking cold.

Thanks for any thoughts / hints. I hope this is not the start of a terror story similar to what I was running into with my Touareg a while back.

On the flip side, the gas Q5 is running just fine, with no issues. I seem to have bad luck with anything diesel-powered.
Age of vehicle? I would look at the gearbox & for a start change the ATF and ensure the level is correct. Drain & fill use VCDS to monitor the temp & add fluid as required.

The internal filter should be clean if however it isnt then that is a clue to as are the magnets on the oil pan. The ATF expands as it warms which may disguise a fault noticable when cold. Start simple 48k isnt a high mileage so doubt it is wear.
 

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50k is a good time to change the fluids in the diffs and transmission.

When's the last time you changed brake fluid?

And I have had an instance where I was in a hurry and didn't let the engine warm up fully so it idled high and stopping was harder.

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Discussion Starter #5
Thank you for the feedback @Troystg, @capese21, and @New2Tregs !

50k is a good time to change the fluids in the diffs and transmission.

When's the last time you changed brake fluid?
We had the car for close to 2 years, and there were no diff, transmission, and brake fluid changes in that period of time. The whole pandemic obviously cut the driving a lot, so we only put about 6k miles in these 2 years between her and me. I was reading a bit and there are claims that the transmission is supposed not to have fluids changed at all. Smells a bit of marketing BS, to be honest.

And I have had an instance where I was in a hurry and didn't let the engine warm up fully so it idled high and stopping was harder.
For experiment I let it idle in the morning today to get into operating temperature before driving out for a quick run and the brake issue was not observed. There was still the reverse to drive shift jerk, but at least the brakes do not freak me out.

Age of vehicle?
2016 Q5 TDI, close to 48k miles on odo at this time. Close to 2 years with us for the time being and has been problem free until now.

I guess the thing to look at is what is the engine RPM when this occurs.
When this happens, the engine is most of the time on 3rd gear, and downshifting. Apart from downshifting, I do not notice any strange problems. I am on stock TCM downshift map, my upshift maps are slightly modified to extend the duration of 5, 6, and 7th gear a bit in D mode, but that should not affect the way the engine downshifts on low end gears. No changes to temp curves, fill ratios, etc.

I know if I don't wait until my engine RPM settles down to ~650-700 when cold I get the same braking effect initially.
Could be possible the engine isn't going to it's low idle setpoint correctly or in time.
If you get the same kind of experience (I assume on Tuareg) then it might be just engine characteristics, since Q5 TDI block is the same (or very similar). I know we did not notice this behavior for the first 15 months or so, and it only started showing recently, once we crossed 45k miles on odo. Not sure if this is related at all, but my first thought was on transmission behavior.

Being you didn't mention it, I'm guessing you have no CEL on?
No CEL, no transmission issues, no errors on VCDS. I also scanned it under all tools I have access to, and no current and no recorded and cleared errors as far as I can tell. Nothing in the scans indicates any problems that sensors could potentially detect

The internal filter should be clean if however it isnt then that is a clue to as are the magnets on the oil pan. The ATF expands as it warms which may disguise a fault noticeable when cold. Start simple 48k isnt a high mileage so doubt it is wear.
I assume the transmission oil filter? Either way any work on transmission fluid replacement will need to be done in a shop, since I am not prepared for that (no tools, no space) for it. Seems like I will need to call in to the local shop specializing in German cars. I do not want to do do it in the dealership and overpay 5 times for the work done.
 

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I bought my 16 Treg with ~48 or 49k miles on it. First thing I did was change all of the fluids.

1. I don't know how long it sat for the diesel gate fix.
2. I don't know how much towing the previous owner did.
3. I don't know if they had fluids changed and used inappropriate ones.
4. If I service it and change fluids at 50k I can drive it worry free(fluids anyway, it is a VW so there will be plenty of other issues) until 100k.

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Discussion Starter #7
Sounds like a very good point - having bought it at dealership, I assumed they would have done it but obviously - that is just wishful thinking. I will call in the shop and get it scheduled for next week. Much appreciated @Troystg
 

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"I assume the transmission oil filter? Either way any work on transmission fluid replacement will need to be done in a shop, since I am not prepared for that (no tools, no space) for it. Seems like I will need to call in to the local shop specializing in German cars. I do not want to do do it in the dealership and overpay 5 times for the work done"

Yes drop the pan. The filter is replacable and on mine it was clean at 60k. An ATF change can be done on the drive. VCDS is required to monitor the temp. Its is straight forward enough. imho with any auto gearbox issues always check the fluid level / condition first.
 

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There is a FANTASTIC thread on here about the two bucket flush.. WELL worth the read. I will be doing that at 100k but a simple ATF fluid and filer service is all I did at 50k.

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I get the feeling that your downshifts might be hanging up. Have you done a trans reset ?
 

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Discussion Starter #11
your downshifts might be hanging up. Have you done a trans reset ?
If you mean the whole press the accelerator for 30 seconds with the car on but engine not running dealio, then yes, I did, several times - it does not remove the issue, unfortunately. All I get is re-learning cycle where the transmission does not know me really well, but that is all. The whole engine vs brake effect is still there, which tells me it has little to do with the shifting points, but more with mechanics.
 

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You dont think the feeling that its fighting against you braking could be that its hanging in 2nd instead of down shifting to 1st ?
 

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Discussion Starter #13
It might be, but when it does finally stop it goes down all the way to 1st, as expected. And if does hang, I am not sure how I would observe that - via logs of sort?
 

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You dont think the feeling that its fighting against you braking could be that its hanging in 2nd instead of down shifting to 1st ?
Mine doesn't downshift to first until under 5 mph. It stays in 2nd until an almost dead stop. The engine has plenty of torque so it saves fuel by staying in a higher gear.

So I wouldn't consider "hanging" in second a negative.

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Personally I don't see that 5mph is a milestone of any significance in this case but then we are all just speculating in an effort to assist. My money is on a clutch pack/valve body...time will tell
 

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Discussion Starter #18
I did some more careful testing today in the morning and it sees to be somehow associated with 3rd gear hanging too long and not downshifting to 2nd correctly. It just does not feel right.
 
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