If the fluid is full of bubbles or is foamy, the transmission is probably overfilled with ATF. Other causes include using the wrong type of ATF or a plugged transmission vent.
REF:
http://www.aa1car.com/library/atf.htm
Bubbles mean that you have overfilled it with transmission fluid. It churn up the fluid and becomes frothy.
The ATF dipstick is located on the Left rear of the engine near the OIL Dipstick
You use a funnel and pour the atf down the transmission dipstick tube.
Add ATF through the transmission dipstick tube. Check the ATF level with engine running and the transmission in park. Check level often as you add fluid with the dipstick until it reaches the "full cold" mark. Type of ATF you should use is written on the dipstick.
Volkswagen does not want you taking labor fees away from it's dealers so they removed the dipstick. You need a scantool to properly top off the atf.
you add atf into the tube that houses the dipstick. you will have to use a funnel but it works.
If you are installing a new or rebuilt transmission and converter, pour 1 qt of ATF into torque converter before assembly. Add 4 qts of ATF after installation thru dipstick tube, start engine and then add aprox 7 qts ATF into dipstick tube until reading on dipstick says full.
It should tell you on the transmission dipstick.
For an automatic transmission, check the fluid level on the ATF dipstick. Refer to your owner's manual for the location of the dipstick.If the level is low, use a funnel to add more ATF by pouring it into the ATF dipstick tube. Be sure to use the right kind of ATF. The new "D/M" ATFs can be used in most cars.
Examine the transmission dipstick. It will tell you what ATF to use.
Remove the dipstick from the automatic transmission dipstick tube and read it. It will tell you what type of ATF to use.
thru the dipstick tube using a funnel with a skinny end