Problem with TIP or drivetrain at highway speeds

[G0to60]

This issue has happened a total of three times. I'll try to write out all of the symptoms and what was going on. 2002 allroad, 2.7T, TIP, 175,000 miles

A few weeks ago I was driving on the freeway going around 55mph or so. There was a slight incline and I wasn't accelerating but holding around that speed. All of the sudden it felt like I tapped the brakes really hard and very fast. Just a quick jolt. I let off the gas immediately and do the look around the gauges and the mirrors to see if any warning lights popped up or if I hit anything. I couldn't see anything out of the ordinary. I was very low on gas at the time (5 miles left according to the read out and the needle was tickling the last red line) and I thought that maybe with the incline a little bit of air caused the engine to sputter slightly. I go and fill up with fuel and am on my way with no issues.

Fast forward to last night. I'm driving from Portland to Seattle and just got on the freeway going around 60mph. The same thing happens but I have a full tank of fuel and it wasn't very low when I topped off (about 1/4 tank). It felt like something with the transmission or drive line. I ease off to see if I can feel anything else but it just continues nice and smooth. About 45min later we are getting back on the freeway from a rest stop and it does it one more time at about 70mph but a bit more violently. I happened to be looking at the gauges and the PRNDS flashed briefly and the revs went up to 4k from 3k and just as quickly back down to 3k rpm. The rest of the trip up to Seattle and back was uneventful with no more symptoms.

I have a generic OBD bluetooth scanner that I use with the Torque app on my phone and it was plugged in at the time. I scanned for codes and nothing showed up. I then unplugged the scanner for the rest of the trip.

Now, here are some of my theories on what happened and I'd like to know if I'm on the right track.

1. Possible torque converter problem - I'm zen with the fact that this may be the problem. I don't think it is since no CEL popped up but I don't know what a dying TC feels like.

2. TIP computer issue - There isn't any water down there but I think that the computer, for whatever reason, shifted down into 4th very briefly. This would be the cause of the unexpected jolt and increase in RPM.

3. TIP fluid is worn out - I had been planning to change out the fluid when it gets a bit warmer out this spring but I may bump up that timing and change it out sooner. I have not changed the fluid in the 18 months that I've owned the car and I don't know if it's been done before.

4. OBD bluetooth affected something - This is a long shot but I thought that maybe that generic scanner affected something while the car was in motion. I don't remember if I had it plugged in when the first jolt happened but I won't be using that while the car is moving, just in case.

5. CV axle or drive line issue - I replaced the PS front axle last year with one from Raxles but the DS is still original and so is the drive shaft. I'm going to get under the car this weekend to get a look under there.

So what says everyone? Is there anything else I should be looking for or checking out? I'm hoping for the best but planning for the worst. I've found that's the best mentality to have with these cars.

[audifirst]

were you shifting in manual tip or was in D drive
probably torque converter is wearing out .. there is a multi switch located near tranny, but I doubt this would be an issue
but if you haven't change the fluid most likely previous owner didn't do it, I change mine every 60k-70k my car is 14 years old now and no issue with tranny, but everytime I change it is very dark brown color, I think you can probably start saving now for either 6speed swap or full rebuild..

[02 A6 2.7T]

Now, here are some of my theories on what happened and I'd like to know if I'm on the right track.

1. Possible torque converter problem - I'm zen with the fact that this may be the problem. I don't think it is since no CEL popped up but I don't know what a dying TC feels like.
This would be my best guess, but it's usually associated with a CEL and will throw a P0741 code, so may not be the case here... worth scanning with a full Ross Tech VCDS...

2. TIP computer issue - There isn't any water down there but I think that the computer, for whatever reason, shifted down into 4th very briefly. This would be the cause of the unexpected jolt and increase in RPM.
It may be dry now, but it could be / have been wet under the carpet in the past

3. TIP fluid is worn out - I had been planning to change out the fluid when it gets a bit warmer out this spring but I may bump up that timing and change it out sooner. I have not changed the fluid in the 18 months that I've owned the car and I don't know if it's been done before.
worth a shot with the high mileage on the vehicle

4. OBD bluetooth affected something - This is a long shot but I thought that maybe that generic scanner affected something while the car was in motion. I don't remember if I had it plugged in when the first jolt happened but I won't be using that while the car is moving, just in case.
...definitely a long shot ... I can't envision any scenario where it could remotely affect the TIP controller ...

5. CV axle or drive line issue - I replaced the PS front axle last year with one from Raxles but the DS is still original and so is the drive shaft. I'm going to get under the car this weekend to get a look under there.
No mechanical driveline issue would cause a temporary increase in RPM along with the flashing lights

So what says everyone? Is there anything else I should be looking for or checking out? I'm hoping for the best but planning for the worst. I've found that's the best mentality to have with these cars.

^^ my best shot

[Castor Troy]

when you do the fluid, my recommendation would be to drain and fill, drive around for a couple weeks, then drain, replace the filter, and refill. when you drain the fluid, you only get 4-5 quarts out, and the 5hp19 has a 9.8 quart capacity. doing the drain/refill/drain again procedure ensures you have the most clean fresh fluid possible, short of doing a full flush which i wouldnt recommend.

eta: my s6 was having similar symptoms. driving down the highway, it would downshift HARD and then immediately shift back up. scotty explained to me that basically the TCU was seeing too much slip in 5th gear and shifting down. i did the fluid and filter and havent had a problem in 20,000 miles (my s6 is up to 153k, original trans knock on wood)

[G0to60]

were you shifting in manual tip or was in D drive

It was in D at the time but for the rest of the trip I shifted it manually. This morning I drove to work (~20 miles) in D with no issues.

No mechanical driveline issue would cause a temporary increase in RPM along with the flashing lights.

My thinking on this was that something in the drive train caught or snagged. This would cause the an increased load similar to going up a hill and would cause the trans to downshift. The snag would release just as quickly and then the trans would shift back to high gear. That's my thought process anyway. It could be pretty far fetched though, I admit.

I will also pull up the carpets and do a more thorough check for moisture just to be sure.

when you do the fluid, my recommendation would be to drain and fill, drive around for a couple weeks, then drain, replace the filter, and refill. when you drain the fluid, you only get 4-5 quarts out, and the 5hp19 has a 9.8 quart capacity. doing the drain/refill/drain again procedure ensures you have the most clean fresh fluid possible, short of doing a full flush which i wouldnt recommend.

eta: my s6 was having similar symptoms. driving down the highway, it would downshift HARD and then immediately shift back up. scotty explained to me that basically the TCU was seeing too much slip in 5th gear and shifting down. i did the fluid and filter and havent had a problem in 20,000 miles (my s6 is up to 153k, original trans knock on wood)

Will definitely do this and I'm glad that this isn't a unique problem and seems to be remedied for now.

Thanks for the feed back.

[audifirst]

here is how my tranny oil look like after 65000 miles / 100000km on the right,
on the left fresh tranny oil
this is after second replacement, wish I had photo of the first one, 1/4 inch of sludge was on the bottom of the pan mind you I do towing with my car so tranny is working double

[G0to60]

Yeah, I have a feeling that my oil is going to look like that or worse. We shall see.

[G0to60]

I changed out the transmission oil and filter a couple of weeks ago and things have been great. The oil that came out was most likely the original OEM stuff and it looked pretty poor. The magnets didn't have much of any material on them when I cleaned them up so that was a good sign. I just got back from a weekend trip to Mt. Bachelor and there are a couple decent grades that I had to go over with not a single hitch so the fluid was the right thing to do and was fairly inexpensive ($115 and a Saturday in the garage).

Hopefully this will buy the trans another 50k miles or so.

[JakAzz425]

here is how my tranny oil look like after 65000 miles / 100000km on the right,
on the left fresh tranny oil
this is after second replacement, wish I had photo of the first one, 1/4 inch of sludge was on the bottom of the pan mind you I do towing with my car so tranny is working double

Mmmmmm. You got corona on the left and Guinness on the right... Yum...

K on to op questions. I had an issue with this a few months ago. Same thing but mine stayed in tranny limp mode till I physically reset it through vcds and even then 20 or 30 minutes and it would do it again. Got home did the tranny fluid/gasket replacement and hasn't done it since.

[G0to60]

Well, after some more investigating I think that the OBD scanner and/or the Torque app caused the hiccups that I felt before. I did some experimenting with it and it would also clunk at low speeds when I had the app running. Every time I've had the app going and I've been driving I've had the clunk. I have never had it clunk on me without the app running although I can't remember if I had the app running when I first felt the problem. So just a heads up that the app and/or the OBD scanner may cause some weird issues if you use it while driving.

I still feel it was the right call to change out the fluid as the old stuff looked pretty past it and it was good piece of mind as I'll be putting some good miles on the allroad this summer.