I was driving our 2000 4.2 Tip today on the Interstate when I noticed something a slightly odd humming sound from the drivetrain. I wasn't sure whether it was the engine or the transmission, and it wasn't anything profound enough to make me stop immediately, so I continued.

About 10 miles later, I was home, and when I accelerated from a stop at the end of an off ramp, the transmission shook quite a bit going into 3rd gear and then caught after a few seconds and behaved better. However, in neighborhood street driving, the problem continued. When I got home, the car would barely go up the slight incline into the driveway. Putting the car into Tip mode and trying to force a particular gear doesn't work, as the car ignores the manual selection as if it's sensing that it's inappropriate.

FWIW...

* Today has been by far our coldest day of winter so far, with temps in the low 20s, if that makes any difference to anyone.
* Also, I had an emissions test done this morning (OBDII readout test only, not a dynamometer test) although I can't imagine that made any difference.
* The transmission has had its coding adjusted to provide a bit more pep, but that was done about 10 months ago. I have recoded back to 00002 (which should be the factory default) on the off chance that that's making a difference. See http://www.audipages.com/Tech_Articl...nsmission.html for more on this if you're interested.

VCDS coughed up the following, and I'd appreciate any insights.

Address 02: Auto Trans Labels: 01L-927-156.lbl
Part No: 4B0 927 156 BS
Component: AG5 01L 4.2l5V USA 1414
Coding: 01032
Shop #: WSC 02325
VCID: 79F250EF495F
1 Fault Found:
17117 - Gear 3: Incorrect Ratio
P0733 - 35-10 - - - Intermittent

 

This might help.


http://www.helpforcars.net/obd_codes/p0733_audi.html

 

Whoa. Very impressive. Thank you very much.

Am I correct that on the A6 the trans fluid is added from below as shown at http://www.blauparts.com/audi/audi_f...nsmissionfluid and that there's no way to add transmission fluid from above the engine?

Anybody used the flush/fill kit at http://www.blauparts.com/proddetail.asp?prod=F2A1004-C ?

What are the odds that the problem is just a low/dirty fluid issue vs. something requiring a major transmission service?

There HAS been some minor fluid leaking under the car recently; is it worth asking my mechanic to try just to top-off the transmission fluid before going through a whole song and dance to replace the fluid and pan gaskets, etc.?

 

Depends on how long since you last replaced the fluid, filter, pan gasket, etc.

The 2K4.2 needs to have trans fluid replaced (IMHO) about every 40-50K miles..you'll agree when you see what comes out of the trans! If, OTOH, YOUR trans fluid comes out crystal clear as the day it was put in (check it with a clear glass of your new fluid) you can extend the fluid change. You won't.

Yes, fluid is added from below. It takes a j-hook shaped hose or a piece of tubing that goes over the lip to fill it..and temperature of the trans is important. Too hot and you'll underfill the trans, too cold and you'll overfill it.

Can't tell for sure what is going on, but it won't hurt (other than the price of the fluid, filter, parts and labor) to try topping off the trans...the mechanic can take a sample of the fluid and see what it's like at that point and then dump the trans fluid, remove the pan and clean it, etc., change the filter, and refill.

Get someone who's done this before with an audi vag-com to monitor trans temp while refilling.

 

BTW, 4B0 927 156 BS is a TCU IIRC. It might be something as simple as a TCU gone bad..there's been a few of them on this forum.

But changing trans fluid should be a 50K mile rite of passage anyway.

 

If I run the TCU through its paces using the test mode on VCDS, and all the solenoids click on command, doesn't that indicate that the problem is more likely in the transmission itself and not the TCU? I thought when VCDS called out a part number like that, it was just stating in which control unit the offending code was being stored, and not necessarily that the part itself of said part number was where the problem was.

What color is Audi trans fluid (so I can check my garage drips)?

And where is the TCU located in the car?

Thanks for all the info, SJB.

 

Sounds logical, at least the TCU is giving commands and the solenoids are clicking/operating. That leaves out the possibility of clogged passages or checkballs. Dunno if this ZF has checkballs but most ATs do.

IIRC the TCU is under the rear carpet, driver's or pax, don't know. Bentley component location will tell.

Fluid color is, well, fluid, depending on what was originally put in the trans. For comparison, Pentosin ATF for Audi is light brown. One source:

http://www.ecstuning.com/Audi---/ES1087/

or google G 052 162 A2 and shop around.

Bummer that it isn't red like other ATF. Would be easier to ID.
Also consider changing lubricant in the front and rear diffs.

 

As you can see from this link to posts the D2 model area -

https://www.audiworld.com/forums/sho...0#post24093800

I did the fluid and filter change and did not have any improvement.

I hope you have better luck than I did.

HTH.

fwiw - my local Napa Auto parts carried the Pentosin ATF-1 trans fluid for $15.99/liter

 

Thanks much. I will continue to investigate to see if I can pin down exactly what it is that's causing the trouble. At least there's only 3rd gear slipping, unlike some other folks who seem to have had multiple gears go out all at once. I'm hoping it's something simple, perhaps related to the extreme cold that just hit today.

The stupid car is only worth $8000 and it would be a shame to spend a ton of money on a major repair to keep it running at this point. We're getting a 2012 A6 no matter what -- I'm starting to think they can't get here soon enough (anybody know when the dealers can start taking orders?).

 

Had to take the car up and down the block last night to test new brake pads, and in doing so, the transmission problem appeared again. When the transmission slipped badly, I noticed that the gear shift indicators (in the red LED panel in the center of the dash) all turned red in a solid bar. I turned off the car and restarted it, and the redness disappeared and the indicators appeared as they always have. Any meaning to this?

Also, the car seems to run fine in reverse. Any interpretation to this?