ZF and Power Steering Flushing

A6 All/ S6 All
#1

I have searched the forums a good bit but not have a definite answer. I currently have the front bumper off the car and core support hanging, I have access to the star bolt holding in the power steering cooler in front of the ac condenser. If I am to flush would this not be the best place to drain from? Thinking of putting a bucket under this and turning the wheels while in the air engine off to pump out the fluid? I am slightly naive on the best practice for PS flush…

Now regarding the ZF flush, my trans imo, shifts perfect, car has 130K on it. I would like to flush before it is not shifting perfectly. So is it true that I need to loosen / drop the exhaust to remove the trans oil pan?! Any tricks?

https://12v.org/urs/C6%20S6%20ATF%20Fluid%20Change.pdf

This might make me wait to do this…

#2

It may be best to leave it alone while it’s working fine. I didn’t have my fluid flushed until the Mechatronic unit failed. I think it’s a catch 22 when it comes to whether or not a flush with help or hurt the performance of the trans. Maybe some other members that have had it done prior to a failure can give you feedback on their experiences.

#3

I know it was “more risky” with the 5HP19 whether or not to do a trans flush but am not familiar with this trans.

#4

You can do really well by just changing out the fluid. I would suggest you just empty the fluid and refill. Pulling the pan requires you take down part of the exhaust header. Its a bit of a pain to mess with the pan.

#5

I agree a flush may be beneficial as it leaves about half the fluid in there. But in the future, I will drop the engine to replace the cats with test pipe and at that time I can do the filter in the trans.

In regards to the PS fluid, do you think I should drain it from the front there the cooler is? Last winter it would whine during startup so I was concerned…No noise when fluid was warm…

#6

You can. I just pull the screen out from the resivware and pull out with a turkey baster and replace. I flush it over time. You can really get it in a few drive cycles. Usually when I do a carbon clean I pull fluid when the car comes in. Whatever driving is needed to situate the car then again after start up and again after a test drive. You would be amazed how much fluid you can clean or flush. I know its not perfict. If you really want you can obviously drain from the PS cooler.

#7

The reservoir strainer does not seem to want to come out for me. Any tricks? I don’t want to break it.

#8

My thoughts on atf flush / change. First the basic concept of a “change” and a “flush”.

Change = drain oil from plug, if any > drop pan and filter > install new filter > reinstall pan > fill up to spec level in spec temp. End result = less than 50% of oil was changed, new filter in place.

Flush = take to mechanic with flush equipment > they connect machine into trans cooler/heat exchanger > machine flushes oil > they disconnect machine.
End result = 99% oil changed, old filter Inside.

Of course, they can also do both if asked for.

Then, what is best practice. IMHO, YMMV. Etc.

If transmission works flawlessly and you have checked fluid is like new. > Flush and change filter.

If transmission works flawlessly but oil is not perfect anymore. > Change.

If transmission is slipping, clunking, etc. Maybe, carefully… > change… but if performance degrades, you are headed into a trans rebuild.

If your transmission is allready shot and you flush. Chances are, you won’t get into gears anymore, because all the clutch friction material that was suspended in the oil, is now gone = full rebuild with reinforced clutches and a TCU update = happy camper :smile: