Checking Automatic Transmission Fluid

It's supposed to be filled for life. Great, but if you suspect a leak there's no dip stick or fill tube, and there's no warning sensor. Someone else has posted instructions for changing gear oil in what looks like a manual tranny: Changing the Transmission Gear Oil

If your transmission does strange things while the car is turning that's a sign that the fluid could be low and is sloshing away from the suction filter.

The ATF level is checked by removing a check plug when the transmission is cool (30 degrees C -- if you've driven it in the last several hours it's probably too hot to do this. I checked mine an hour after driving and it was still at 68 C). The car is then started. Once the temperature reaches 35 C if it begins to leak out you can replace the plug and are finished. If it reaches 40 C without leaking out then add ATF through the check hole until it begins to spill out and then seal. Bentley specs 50C for warm countries.

Required:

• Pentosin ATF1 or something similar (~$15/L - I found some at NAPA). Audi spec for my car is for: G 052 162 A2 (A2 designates 1L size bottle).
• Oil suction gun ($10) to inject ATF through a tube, or possibly a long tube connected to a funnel held high...
• 17 mm hex 1/2 in. drive. Torque check plug to 80 Nm (~60 ft lbs). I had to go to several parts stores before finding one (a 3 piece set ~$15, I think from Pep Boys ...and Advance has a 12 point star bit set for $8, for CV-joints). 
• New check plug seal: 01V 321 379 ($3) (if not check for leaks down the road and replace if needed when car is cold)
• Vag-Com or similar scanner to monitor temperature of your transmission. If you do this on a very hot 100F day you might be able to get away without measuring??? Both too much and too little are bad.

The plastic cap with the fill hole snaps onto the pan. Be careful not to hit it too hard or it could come off requiring pan removal.

Cardboard, rags, and a catch pan. Still this was a lot less messy than an engine oil change. The smaller plug is the drain plug. If you remove that to change the ATF (up to 3 L required. Total capacity is 9L so you're still only changing a third by draining) Bentley manual states the drain plug should be replaced (just the o-ring seal is replaced for the fill plug).

Injector pump. Ramps on slight slope (check for level tranny pan) backed up by jack stands (you're way under the car and those ramps looked like they were flexing a bit).

Here's some info I compiled from the Bentley manual for the A4 (B6). Typos possible--please verify for yourself. Only the automatic tranny has separate oil housing for the front and center differentials since they use a different oil (this table does not apply to CVT):