A4QuattroV6

So those trans cooler lines to the radiator are garbage. Can I run an external cooler and what is the trans fluid capacity of the radiator so I know what size I need? thanks.

Prospeeder

Yes you can, its just low pressure flow so clamps and splices will work fine. I would get a rather good size cooler. Downside to doing this is, in very cold temps, the transmission will never be able to reach operating temp and would wear out quicker or hold shifts longer to try and warm it up. The cooler hoses rarely leak, just get a set off a Passat or A4 at the wrecker.

A4QuattroV6

So cooler isn't always better in this case?

A4QuattroV6

I plan to mount it to the rear fuel rail holes that used to mount the back of the central engine cover and put a WRX hood scoop above it. So it would look like a wrx only instead of an intercooler, its a trans cooler under the scoop.

turbo510

Cooler isn't always better- in most cases. The hotter a cylinder, piston head, and combustion chamber are, the more efficient the engine, up to limiting factors of lubrication, metal strengh, detonation. Engine oil and ATF will develop sludge from water condensation unless heated enought to drive the moisture out. That's the problem with an ATF cooler that cools when it shouldn't, you might actually do more harm than good.

A4QuattroV6

Can somebody give me the capacity of trans fluid that the radiator holds? Audi didn't see fit for a dip-stick so everything has to be pre-measured.

turbo510

Nothing has to be pre-measured. Don't bother measuring how much drained out, either. The check/fill port is up in a recessed hole for a reason- it's a stand pipe, where the top sets the proper running level of the ATF. You get the car fairly level, and add fluid untill any more just runs out, and the level is set. Plug it up and shut the engine off and you're done.

A4QuattroV6

so you do it while the car is running? does it need to be in gear or does the fluid pump run automatically?

turbo510

The procedure is to fill as much ATF as it can hold with the engine off, then start it up. The pump always works when the engine is turning, as there is a direct connection bypassing the hydraulic vanes of the torque converter. The pump will suck fluid from the pan to fill the system, leaving more room for additional ATF. You continue to add fluid until it can take no more (it just dribbles out of the fill port). The gear position is not so important, but you should shift between Neutral, Drive, and Reverse at least once to get all the clutch packs purged of air. Then, using VAG-COM to verify temp in the 35C ~ 45C range, or your hand on the warm but not too-hot-to-the-touch pan, put the fill plug back in. Finally, turn the engine off.