Transmission woes (5 speed tip)

[A4 Quattro]

Sorry in advance for the long post.

I bought a 3.0 B6 with a tiptronic just shy of 7 years ago. Over the time that I've owned it, I've always noticed third gear was a little hit or miss. It would often jolt when going into third (from 2nd and 4th). Over the last couple years, it's gotten progressively worse. Often times, I'll shift from 2nd to 3rd, the car will rev up to 5 or 6k, and jolt like I'm hitting a brick wall, and stay in 2nd. I just try again, and it'll go right into 3rd. This has only ever been an issue when the car gets hot. So it's minimal at most all winter, but very prevalent as soon as spring and summer arrive. The car has never thrown a code because of this.

A couple weeks ago, it jolted and stayed in 2nd, as has become almost expected at times, so I tried again and it missed again, and put my transmission into limp mode. The PRNDS lights all lit up, locked me out of manual mode, and wouldn't even try to shift out of 2nd. 1st, park, neutral, and reverse all still worked. I parked the car in a nearby garage, reset the ECU, and let the car cool down. An hour or two later, I was able to drive "normal" again, though it was still fairly rough.

Since resetting the ECU that night, and keeping driving to an absolute minimum, I have had zero problems shifting into any gear, even under a slightly too aggressive acceleration. I've been looking into replacing/rebuilding the tip, but a friend pointed out that the TCM may be a possible culprit, seeing as the problems have subsided after resetting the electronics.

So I guess my question for you transmission gurus is could the TCM be to blame? Granted the problems that have occurred are mechanical, but mechanical parts controlled by a computer.

I can't be the only person who's had this issue, though searching hasn't provided much on this problem. Any insights/thoughts would be helpful.

[yanni6556]

Try using basic settings in VCDS to cycle the solenoids in the valve body for a few seconds at a time and do a tb calibration while your there.

I did that the other day and the transmission is shifting perfectly except sometimes a rough downshift in 3rd (very rare now). I think it mostly has to do with the way the gearbox is coded and the fact that the electronics are starting to get quite old. The problem still was there after a rebuild btw, rebuilt my tip around 20 thousand Ks ago and the valve body was checked over and improved at the time.

Otherwise yeah just check your computer to see if its wet/damaged and go from there.

[seanf86]

sounds like it could be a valve body problem, have you changed the fluid or checked the level? I'd start there first since it can be a reasonably priced DIY. Could be the pressure regulator. Trans go makes a repair kit http://www.transgo.com/products.php?...product_id=267

I've got a 1.8t tip that bangs 3rd gear I'm going to try this, also check for codes for the fluid temp sensor, that will cause harsh shifts if the trans thinks the fluid is too hot.

[Gin+]

sounds like it could be a valve body problem, have you changed the fluid or checked the level? I'd start there first since it can be a reasonably priced DIY. Could be the pressure regulator. Trans go makes a repair kit http://www.transgo.com/products.php?...product_id=267

I've got a 1.8t tip that bangs 3rd gear I'm going to try this, also check for codes for the fluid temp sensor, that will cause harsh shifts if the trans thinks the fluid is too hot.

Hmm, rock auto has that listed for $50 shipped. I occasionally have a rough time with 3rd gear as well. I'd be curious to give that a try.

[Turbo510]

The car has never thrown a code because of this.

Do you mean no transmission codes too, because if the TCM went to limp-mode, it would almost certainly log a code for something.

If warm weather influences this behavior, then maybe ATF viscosity is the issue. A worn pump or internal seals might allow the fluid pressure to get too low. Or the temperature sensor inside the transmission may be giving a reading that triggers limp mode. You don't mention a fluid or filter change, which should be done about every 40K miles. I would change the fluid using Valvoline MaxLife ATF, which might help with hardened seals, if that is the problem.