rs4-380

I am on the road and haven't had a chance to do much investigation (vag-com etc) but thought I would post here in case anyone had seen it before.

I've got a 200k mile a6. The transmission isn't fresh as a daisy, but it works, and I try to work with it not against it. That being said, tonight on a 3 hr drive it did something I have not seen it do before. With cruise control set at 75mph, it downshifted to 4th on an uphill grade but would not upshift back to 5th after cresting the hill. I had to move it into tip mode and upshift to 5th (which it did fine) manually. It then happened twice more when braking lightly at around 65mph on a level grade. At that point, I put it in tip mode and kept it in 5th gear. The car did fine up the rest of the hills at speed. After getting off the highway, I only had ~5 minutes of city driving, but nothing else seemed to see abnormal.

ANy input?

rs4-380

forgot to mention, it is abnormally hot and humid here (as with most places), but a year ago the car was sitting in 90+ degree stop and go traffic without ever having this issue.

4Driver4

When was the last time the fluid and filter were changed? Ever check the fluid levels in the trans?

rs4-380

did fluid and filter close to 2 years ago (35k miles ago). Haven't had a chance to check it but it is first on my list when i get home. Unfortunately it is 4+ hours away in 100+ degree heat through hills and ****ty traffic.

4Driver4

I'd check the level. Definitely good that you changed it. Heat shouldn't be a big factor. The trans cooler works pretty well.

rs4-380

so I said checking the fluid was first thing on my list, but... instead I got home, put the a6 away and got the s5 out. will report back tomorrow when I get a look at it.

rs4-380

No codes, checked the level and topped it off but it didn't really take much (like less then 1/4 of a quart). The issue did pop up about halfway into the 4 hour drive home. It was also doing it in more then just 5th gear (ie downshift abruptly, then not upshift). In all cases tip mode would get the car to upshift without problem.


Anyone experience anything like this before?

question.com

Happens to me all the time. Only on hot and humid days. I've learned to just use tip on those days. Took it to the shop. No codes. Work calibrated the throttle body, and nothing.

rs4-380

the issue still exists. I say it is a 5th gear issue but I am not sure it's limited to just 5th gear. I notice it the most when on the highway with cruise control. It won't happen right away, but after say 15-20 miles or driving, if the car goes up a big enough hill (or the engine comes under increased load), the engine RPM will jump ~200 from say 2900 to 3100. I'm not more alert to that situation and kick the transmission into tip mode, at which point it falls back to 2900. I haven't had it downshift again but I am assuming if I didn't put it into tip mode it would. If I leave it in tip mode I never have any issues.

I'm almost thinking its an issue with the lockup on the torque converter (which causes the 200rpm "slip" but not a downshift. I don't know enough to figure out why it doesn't happen when in tip mode though.