audisowner

Had a chance to drive my wife's 99 A8 (102K miles) for an extended trip. The tranny has been experiencing significant/increasing hunting/shuddering problems when in Auto (D) mode. I drove the car in tiptronic mode (all gears) for a couple of hours and the tranny/shifting was absolutely perfect.

Can one of the tranny guru's explain what's going on, and your best guess as to the remedy. I understand the TC and valve body rebuild is the usual recommendation, however I'm at loss to understand how it could work perfectly in tip mode??? Any comments welcomed. Tkx.

marcodant

the reason it works perfect in tip mode is it does not have to think for itself you are doing it and I am sure keeping the RPMS up higher then in auto mode. Let the RPMS drop and IT most likley will hunt and shudder, But after a TC and VB rebuild you should have that new tranny feeling again.

ScotD

The trannys in A8's are adaptive, and "learn" your style of driving. Resetting this may help.

<a href="https://forums.audiworld.com/a8/msgs/85952.phtml">WOT procedure</a>

Angus Beef

clean with CRC QD and put some dielectric grease on it. But it does sound like its time for a new TC. It didnt hunt in tip bc the TCU wasnt allowed to change gears without you asking for a change.

Angus Beef

^^^^^ what he said.

audisowner

Thanks very much for the tip and recommendations from others.

Here's what I don't get... If the tranny shifts normally in tip mode (I will check it again at low RPMs), wouldn't it indicate either a TCU problem or a "sensor" (torque/speed) problem instead of TB/valve body?

Angus Beef

hook up the VAG-COM and see if its throwing codes.

marcodant

I had the same problem after my tranny was rebuilt. The TC had to be pulled back out and a new (rebuilt one) put in and problem gone. In Tip mode you are in more control but I bet if you run it at low rpms you will have the same issue. My two cents is have a shop look at it and see what they say but I bet it is a TC rebuild only. But I would also suggest the VB checked and rebuilt too and change the fluid and filter before something internal breaks.

audisowner

just fyi - tried the WOT "reset" of the TCU per ScotD with no difference with hunting/shuddering (thanks for the idea tho...).

Still no problems in tip mode even at low RPM's (might be very slight in 4th around 1100-1200 RPM). Will check codes with the VAG-COM when oldest son returns with it...

So, it looks like we'll do the TC rebuild first.

1.Is Eriksson Industries (Old Saybrook, CT) the best place to have the TC rebuilt?

2. Thinking about the next step, can the valve body can be rebuilt with the tranny in the car? or should it be rebuilt when we have the tranny out.

Thx in advance.