Gearbox Problem in Passat 1999

it could be the torque converter. something is failing around that area.

Is there an ECU just for the tranny? If there is, have it check out.

If no external leak and the transmission fluid colour looks white, the problem belongs to the automatic gearbox oil cooler. The oil cooler has broke mixing the gearbox oil and coolant causing this milkshake. It's a small radiator core type oil / water heat exchanger. It is cracked inside and transmission oil is mixed with engine coolant. Because the transmission oil pressure is greater than engine coolant pressure, the transmission fluid level drops. See also the coolant colour inside recovery coolant reservoir inder bonnet! It could be like this:


The automatic gearbox oil cooler type oil / water heat exchanger (oil cooler):


In the picture above the transmission oil pan was removed for oil filter replacement.

you have effectively got two gearboxes in the car.1is a normal auto (D) ON THE FLOOR then you have + and - for the "manual" take your pick....now here is the clever part,if you put the car in auto "D"and dont touch the gas the car will accelerate to about 35 on the flat.and will change as per a normal auto,if then when you stop you put 1/3rd gas pedal and hold that position it will go right upto about 65,stop then puit your foot right to the floor (kickdown)and the car will fly...stop...you have just reset the gearbox..try and keep to 1/3rd gas for about 25miles and you will see a big difference in gear changes/revs (smoother)but boring....

this is not a weekend mechanics type job because you could damage something else taking it out.best advice is to fit a manual gearbox which here in spain you could buy from a accident damaged car with the flywheel and clutch and starter motor for around 300€ need to change the drive shafts as well i think