DIY ZF8 Fluid+Filter and Front+Center Differential Change

[Discipulus]

There are a few DIY's out there already but they seemed incomplete and information was scattered, so here is a post combining all the info I could find along with some tips and tricks I found helpful along the way.

*Notes*
1. You will only drain/fill about 5L of fluid out of the 9L within the transmission. To get more than this, you'd need some kind of special pump/tools not covered in this guide.
2. Some folks are doing just a fluid drain and fill, which I do not recommend. ZF recommends changing the fluid AND filter every 80,000-120,000 km (50-75k miles) and I'm inclined to agree after seeing how black the filter was when I changed mine at 84,000 miles.
See ZF's official guide and service interval info here: https://aftermarket.zf.com/remotemed...p-50130-en.pdf
3. Since you must remove the cross brace,transmission mount, and cross member, It makes sense to also change the Front/Center differential fluid while you're in there, as those are much easier to accomplish with those parts removed to expose them.
4. Refill is done while the engine is running - you must be comfortable with this and employing safe practices before attempting this job (using jack stands or a lift, etc).
5. Don't over tighten the transmission pan bolts... they're aluminum. We're talking just 35 inch-lbs of force here, like barely more than finger-tight.

Parts List
Transmission Service Kit
https://www.ecstuning.com/b-assemble...t/g060162a2kt/
Per ZF - do not use any fluid other than ZF Lifeguard 8 fluid. I'm sure there must be a compatible alternative but I chose not to risk it. Plus, the ECS kit made it super easy and not have to hunt down individual parts.
If you don't get the kit, just make sure you obtain all components (Fluid, filter, gasket, new fill plug, and 12 new bolts, none of these are reusable)

Center Differential (Transfer Case)
- 1L of Audi specific oil (G055145A2). **Contains friction modifiers not found in common GL5 75w90 gear oil. Do not use a substitute**
- Drain plug: 01V409057A

Front Differential
- 1L of any GL5 75w-90 Synthetic gear oil, or Audi fluid if desired (G052145S2)
- Drain Plug: 01V409057A (unconfirmed part#, I didn't replace this on mine)

Cross Brace TTY (Torque To Yield) bolts
B8.5 - https://store.034motorsport.com/x-br...ft-models.html
(for B8.5, use B8 bolts if pre-facelift model)

Tools List
- 4 x Jack stands (all 4 wheels must be level and off the ground, able to spin freely during refill process)
- Torque wrench (in-lbs or other small scale torque wrench)
- Metric socket set
- Torx bit set (T25 and T40 I think?)
- Hex/Alan wrench set (5, 6, 8, and 10mm)
- Triple Square set (M10, M12, and M14)
- Fluid pump (This or something similar: https://www.ecstuning.com/b-schwaben.../007311sch01a/)
- VAG-COM or VCDS cable (Transmission must be filled at a specific oil temperature with engine running)


DIY/Tutorial links
The best video guide so far: https://www.youtube.com/watch?v=k5PoAb3FkMY
A pretty good writeup: https://www.audiworld.com/forums/a6-.../#post24959970
More info on Differential service: https://www.audizine.com/forum/showt...nge-parts-list
Biggest thread on fluid change so far: https://www.audizine.com/forum/showt...Lifetime-fluid
Torque specs and screw tightening pattern: https://aftermarket.zf.com/remotemed...p-50130-en.pdf

Summary of steps
Procedure – Prep
Best done with car/transmission fluid still warm.
1. Jack the car fully level with all 4 wheels off the ground. Do not use ramps, as the wheels need to spin during the fill procedure.
2. Remove under belly covers
3. Remove cross brace
4. Support rear of transmission with jack and remove transmission cross brace/mount to expose oil pan bolts
- 4 M12 Triple Square bolts on outside
- 4 13mm nuts inside
- 3 M12 Triple Square bolts holding trans mount to transmission

Procedure – Drain
1. Break loose the fill plug – 10mm hex
2. Unscrew drain plug – 5mm hex (expect about 4qt of fluid)
3. Unscrew oil pan from transmission (12 x triple square)
4. Pull the filter downward off the transmission (no screws, just "pops" off). Inspect the pan and filter magnets for chunks of metal. If you have chunks, there's a problem and you should see a mechanic.
5. Clean the pan with paper towels
6. Install new filter (just push up, no bolts or securing method)
7. Install new gasket and reinstall oil pan following bolt sequence guide
- bolts are 4Nm+45° (35 in lbs)
8. Check drain plug for tightness
- plug is 8-12Nm (70-106 in lbs, 6-7ft lbs)

Front+Center Differential notes
(Skip this section if not performing differential fluid change)
This is pretty basic stuff - just drain through the drain plug and fill through the fill plug until fluid runs out the fill hole.
- Tail shaft (rear end) of the transmission contains the Center Differential (transfer case). Use the expensive audi-specific fluid here
- Center differential drain plug can be difficult to locate - it's small but you'll notice it's the only Hex/Alan bolt in the vicinity of the tail shaft.

Front differential guide: https://www.audizine.com/forum/showt...ZF8-automatic)


Procedure – Initial Fill
Initial Fill
1. Fill until fluid runs out of fill hole (about 3qt)
- Install fill plug, hand tighten to snug

Procedure - Final Fill
1. With car in P, and e-brake on, push the brake pedal and start the car. Wait until fast idle ends.
2. Connect VCDS and navigate to Select Module>02 Auto Trans>Advanced Measuring Values>Transmission Fluid Temperature
Temp must be 30°C-50°C, allow car to warm up (continue idling) or cool down (shut car off) as necessary.
3. At correct temp, with e-brake set, Rev engine in P above 2000rpm for 30 seconds to fill torque converter
4. At correct temp, with e-brake set, HOLD THE FOOT BRAKE and shift into R, and D for 10 seconds in each gear. Shift back to P
5. Check temp – if in range, release the e-brake and shift into R, D, M1, and M2 for 10-20 seconds each, letting the wheels spin freely.
6. Check temp – if in range, leave car running in P with e-brake set.
Unscrew the fill plug and fill until fluid starts running out
Replace fill plug – tighten to 30-35Nm (265-309 in lbs, 22-26 ft-lbs)
7. Shut off engine

Procedure – Transmission Adaptation reset
1. Select Control Module
2. 02-Auto Trans
3. Basic Settings – 04
4. Select "Resetting of all adaptation values" from the top drop down
5. "Go!"
6. Select "Erasing of system-specific adaptation values" from the top drop down
7. "Go!"
8. "Done, Go Back"

Take it for a drive. You'll notice buttery smooth shifts for the first drive cycle or so. As the transmission learns and re-adapts the shifting will become more firm and noticeable and may return almost to pre-service shifting feel.

For tuned folks: When I emailed EPL and asked about transmission service intervals, they recommended doing this every 50k miles.
For not-tuned folks: Follow ZF's guideline of 50-75k miles depending on your driving style.

Special thanks:
@tocqueville for parts list
@KwikStix for parts list, tips, and links to the video DIY
@AllroadCorbin for pioneering the first notable thread on this with excellent info
@A4x for the front differential guide


Hope this compilation helps out anyone who needs it so you don't have to look around and research quite so much!

- Discipulus

[Maddog3xx8]

Solid write up!

Sent from my SM-N976V using Tapatalk

[Novarider]

I think you missed a step.

1: Fill until it runs out, insert fill plug.
2: Start engine, fill until it runs out.
3: Monitor temp and do final fill procedure.

That's what it says on the third page of the pdf you posted.

If you skip step 2 you'll be too low on fluid to properly fill the torque converter. IIRC when I did my fluid/filter change step 2 took most of the fluid.

[Discipulus]

I think you missed a step.

1: Fill until it runs out, insert fill plug.
2: Start engine, fill until it runs out.
3: Monitor temp and do final fill procedure.

That's what it says on the third page of the pdf you posted.

If you skip step 2 you'll be too low on fluid to properly fill the torque converter. IIRC when I did my fluid/filter change step 2 took most of the fluid.

I double checked and this is already covered in the "Procedure – Fill" and "Procedure - Final Fill" sections of my post. Both those sections cover steps 1-3 you mentioned in that order. For clarity I've updated the post to reorder it a little and make it more apparent that these steps are important to follow in order. Thanks for the feedback!

[MSq5]

Thank you. Much appreciated. I'm at 62,000 miles (100,000 km) with dual pulley ECU and HP Tuners ZF8 self-tune auto upshifting at 7,000. I'm due per ZF.

[Maddog3xx8]

Thank you. Much appreciated. I'm at 62,000 miles (100,000 km) with dual pulley ECU and HP Tuners ZF8 self-tune auto upshifting at 7,000. I'm due per ZF.

I'm. In the same boat and need to get this done

Sent from my SM-N976V using Tapatalk

[dubgli]

Damn, I've done my transmission fluid and filter twice for the sq5 and a bunch for my vw, I've never spun the wheels in the air.

Wondering if I need to now. Knock on wood, it hasn't been a problem ever but I've definitely missed that step.

Good to know.

- dubgli

[Discipulus]

Honestly it's probably fine without wheel spinning - that's just the only way I could figure out how to shift into D2 (using manual mode), without the wheels spinning it would only stay in 1st gear.

Plus I figured it would be good to have the gears spin around and get lubrication with zero load before driving it.

The difference however is probably minimal.

Damn, I've done my transmission fluid and filter twice for the sq5 and a bunch for my vw, I've never spun the wheels in the air.

Wondering if I need to now. Knock on wood, it hasn't been a problem ever but I've definitely missed that step.

Good to know.

- dubgli

Sent from my Pixel 3 using Audizine mobile app

[Novarider]

I tried to spin the wheels when I did mine but ABS freaked out and wouldn't let me. Next time I'll try it with traction control turned off. Didn't think about doing that the first time.

[EvoToSQ5]

What are you guys doing with the other 4L of ZF fluid from the kit?


Sent from my iPhone using Audizine

[Discipulus]

If I feel motivated I'll jack it back up after a month and drain 4L and then use those extras to fill again. It would effectively be the same as changing 7L of fluid. So you'd still have 2L of old fluid remaining.

Or keep it for the next change and just buy the filter+bolts+gasket and only 1L of fluid?

What are you guys doing with the other 4L of ZF fluid from the kit?


Sent from my iPhone using Audizine

Sent from my Pixel 3 using Audizine mobile app

[Der Konig]

Legend.

I was just looking into doing this. Makes it that much easier, let it get away from me so I am at 100k on original fluid. Oopsies.

[Discipulus]

Yesterday I drained and filled the remaining 4L of fluid that were included in the kit. I'm glad I did because the fluid looked pretty dark brown after just 1000mi of driving since the initial 5L fluid/filter change. I think it's worth it to use the extra 4L and do this to get the fluid as fresh as possible.
In effect, there should only be 2L of "old" fluid remaining in the transmission at this point.

[EvoToSQ5]

Yesterday I drained and filled the remaining 4L of fluid that were included in the kit. I'm glad I did because the fluid looked pretty dark brown after just 1000mi of driving since the initial 5L fluid/filter change. I think it's worth it to use the extra 4L and do this to get the fluid as fresh as possible.
In effect, there should only be 2L of "old" fluid remaining in the transmission at this point.

Did you measure the fluid you were draining and refilled exactly 4L?


Sent from my iPhone using Audizine

[Discipulus]

Did you measure the fluid you were draining and refilled exactly 4L?


Sent from my iPhone using Audizine

Not really - just let it drain until it looked like approximately 3.5L of fluid came out. Confirmed by pouring into a container and make sure it's less than 4L of fluid. If you undershoot you can just open it up and let it drain more. Just be careful not to overshoot. I ended up draining a little over 3.5qts of fluid (which equates to roughly 3.5L)
Not necessary to measure the refill - just fill until it pours out the fill hole, following the fill procedure in the guide. I had maybe 1/3L of new fluid leftover when the job was complete. I'm personally ok with that margin of error - it would be more difficult to measure exactly and get exactly 4L out and back in.

[MSq5]

I like how you did that by doing a second partial drain and fill 4 more liters to further dilute what you couldn't get out the first time. I'll be doing my ZF8 soon as I just hit 100,000 km. I bought a combo pneumatic extractor and dispenser. It's made for automatic transmissions and hydraulic fluid systems. In the interim, I've done oil extraction with it. It works with any viscous fluid. It's the same one used in the first video above.

It's advantage will be that it dispenses, and you can measure how much comes out and how much goes in. When doing the dilute phase, I should be able to draw precisely from the top "fill hole" rather than the drain hole and replace with the same amount. The side of the jug is marked up to 6 liters. It has attachments, one of which is a dispenser nozzle claimed to be for VAG vehicles. We will see.

Thanks for sharing your how-to, not only the mechanical part, but also the VCDS settings for trans temp and adaption. This should be given a "sticky" for quick reference. Everybody with ZF8s should be doing this, especially if tuned.

[Novarider]

I like how you did that by doing a second partial drain and fill 4 more liters to further dilute what you couldn't get out the first time. I'll be doing my ZF8 soon as I just hit 100,000 km. I bought a combo pneumatic extractor and dispenser. It's made for automatic transmissions and hydraulic fluid systems. In the interim, I've done oil extraction with it. It works with any viscous fluid. It's the same one used in the first video above.

It's advantage will be that it dispenses, and you can measure how much comes out and how much goes in. When doing the dilute phase, I should be able to draw precisely from the top "fill hole" rather than the drain hole and replace with the same amount. The side of the jug is marked up to 6 liters. It has attachments, one of which is a dispenser nozzle claimed to be for VAG vehicles. We will see.

Thanks for sharing your how-to, not only the mechanical part, but also the VCDS settings for trans temp and adaption. This should be given a "sticky" for quick reference. Everybody with ZF8s should be doing this, especially if tuned.

IIRC you must have the car running if you want to use the fill port. I seem to remember that if the car isn't running and you pull that plug you'll get a bath in the fluid.

Why not just pull the drain plug? Seems like a hastle and a mess just to save on 1-2L of fluid.

[Discipulus]

IIRC you must have the car running if you want to use the fill port. I seem to remember that if the car isn't running and you pull that plug you'll get a bath in the fluid.

Why not just pull the drain plug? Seems like a hastle and a mess just to save on 1-2L of fluid.

You're right, the engine must be running to fill completely. It's really not that bad, not much harder than an oil change.

Drain from the drain plug
Fill from the fill plug
Start the engine and fill some more and you're done.

Honestly the most time consuming part of this is just getting the dang car up on Jack stands and level.


Sent from my Pixel 3 using Audizine mobile app

[MSq5]

You're right, the engine must be running to fill completely. It's really not that bad, not much harder than an oil change.

Drain from the drain plug
Fill from the fill plug
Start the engine and fill some more and you're done.

Honestly the most time consuming part of this is just getting the dang car up on Jack stands and level.


Sent from my Pixel 3 using Audizine mobile app

Thank you.

[Vehicle 1]

Just wanted to thank the OP for this thread.
I'm used to wrenching on my truck and motorcycle, but not the SQ5. This info makes it less intimidating.

I got everything needed to do this service next weekend.

[Vehicle 1]

I finished doing the transmission service yesterday and not as much fluid went in as it drained out.
I followed the instructions to a T, but I drained ~4.75L, and while following the procedure only ~4.45L made it in.

I am guessing that the car was not PERFECTLY level and the left side was a tiny bit higher.

My dumb question is... would it make sense to just lower the left side of the car a bit to pour in the extra measured 300mL so it fits?
The car is still on jack-stands so it would be easy to do before I finish everything, still need to do the differentials.

[wilmar13]

Is there any reason you can’t run the engine with drain plug pulled to drain more than 5L by forcing it out torque converter circuit into pan? There is no load on transmission really with wheels in air. Just wondering if makes more sense to do that than just change half the fluid.

[djn876]

Is there any reason you can’t run the engine with drain plug pulled to drain more than 5L by forcing it out torque converter circuit into pan? There is no load on transmission really with wheels in air. Just wondering if makes more sense to do that than just change half the fluid.

It would not be a good idea to run the transmission dry or low to try and use the pump to remove more fluid. You are highly likely to damage something. There is a lot more than just gears in there.

Sent from my SM-G988U using Audizine Forum mobile app

[wilmar13]

It would not be a good idea to run the transmission dry or low to try and use the pump to remove more fluid. You are highly likely to damage something. There is a lot more than just gears in there.

Sent from my SM-G988U using Audizine Forum mobile app

I may try to drain it with front lifted and rear down on ground. If it can get 6L out instead of 5, that is perhaps something worth doing for a DIY'er that is using jackstands.

The fill plug is so low, the transmission internals do not need to be submerged to function, and there will be plenty of residual oils in it. I just don't know how the torque converter path works, but perhaps another small risk taken to expand knowledge could be to remove the sparkplugs, put the transmission in gear (with all 4 wheels in air) and turn crank by hand to see if you can get more than 5L out.

[djn876]

I may try to drain it with front lifted and rear down on ground. If it can get 6L out instead of 5, that is perhaps something worth doing for a DIY'er that is using jackstands.

The fill plug is so low, the transmission internals do not need to be submerged to function, and there will be plenty of residual oils in it. I just don't know how the torque converter path works, but perhaps another small risk taken to expand knowledge could be to remove the sparkplugs, put the transmission in gear (with all 4 wheels in air) and turn crank by hand to see if you can get more than 5L out.

The fluid is pumped through and I imagine that pump uses the fluid for lubrication. Agreed it doesn't operate with submergence throughout the entire trans, but there are areas that absolutely need to be filled with fluid whem in operation. Not a good idea either way, how much is OK, and when will damage occur? Who knows. The pump will likely cavitate if nothing else on low suction and probably not function correctly. With the risk being potentially a new mechatronics and worst a trans rebuild it's not worth it.

Just drain what comes out and you'll be good, that's the way ZF says to do it so i really wouldn't be overly concerned about squeezing a little more. The fluid gets to the converter via the mechatronics and various solenoids so what paths are active when I don't know.

Sent from my SM-G988U using Audizine Forum mobile app

[wilmar13]

The fluid is pumped through and I imagine that pump uses the fluid for lubrication. Agreed it doesn't operate with submergence throughout the entire trans, but there are areas that absolutely need to be filled with fluid whem in operation. Not a good idea either way, how much is OK, and when will damage occur? Who knows. The pump will likely cavitate if nothing else on low suction and probably not function correctly. With the risk being potentially a new mechatronics and worst a trans rebuild it's not worth it.

Just drain what comes out and you'll be good, that's the way ZF says to do it so i really wouldn't be overly concerned about squeezing a little more. The fluid gets to the converter via the mechatronics and various solenoids so what paths are active when I don't know.

Sent from my SM-G988U using Audizine Forum mobile app

Yeah, I agree, it was just my curiosity in trying to think of a way to get more fluid out. The factory process is designed around economizing the service time, not necessarily the best thing if you are doing it yourself and will take more time. It isn't worth the hassle and potential issues to turn over engine (manually or with starter) just to get more fluid out.

I crawled under car to measure lower control arm bushing sizes ( figure if I can find right sockets or pipe diameter I can save $400 buying just the bushings, instead of replacing entire arms), and noticed the transmission cooler lines... so I think what I'll do is drain the transmission with front of the car lifted 8-12", then level it and drain ATF cooler opening where there is threaded connection at lowest point in lines just below the radiator. Also I can blow out ATF cooler in case more clutch particle junk is accumulated there. If i get an extra liter out between those two things, it will be worth the small effort. haha

[wilmar13]

Actually I just thought of a way to get the fluid out of the torque converter after thinking about the ATF cooler lines without doing anything that would have anything running dry or low. The fluid from torque converter goes into cooler before it is returned to transmission.

So drain the pan, clean pan, install new filter, put fluid back in that you took out just like standard process. Now instead of just doing the run engine and add more fluid; open up the return line of the ATF cooler and run engine, replacing what gets dumped out from torque converter as you go. Once clean oil starts to come out the ATF cooler return line, you got it all out of the torque converter too. Now just proceed as normal. If anyone is following what I am saying, you just replaced all the oil in your transmission, instead of just half of it. If someone sees a problem here, please stop me, but otherwise I am going to try this. It seems like a good way to get most of it out, instead of half of it out.

[djn876]

Just for clarity, the procedure is not from Audi, it's from ZF (The manufacturer and designer of the trans). They don't do maintenance, they just sell them to the OEMs, so I doubt they have any agenda regarding service times. ZF isn't going to risk the trans and their business to save a little of the car makers time, and these ZF transmissions are in everything from a Dodge Ram to a Rolls Royce.

If you ask Audi, they will say you never need to change the fluid.

As an FYI, the factory manual says the trans needs to be removed to pull the ATF pipes.

I get what you are trying to do, but I think you are just over thinking it. Just replace what you can with the filter and keep doing it every 50k or so and you will be all set. These are great, reliable transmissions, and if you are worried about it, just do it every 20 or 30k instead.

Sent from my SM-G988U using Audizine Forum mobile app

[wilmar13]

If you ask Audi, they will say you never need to change the fluid.

As an FYI, the factory manual says the trans needs to be removed to pull the ATF pipes.

I get what you are trying to do, but I think you are just over thinking it. Just replace what you can with the filter and keep doing it every 50k or so and you will be all set. These are great, reliable transmissions, and if you are worried about it, just do it every 20 or 30k instead.

Sent from my SM-G988U using Audizine Forum mobile app

Audi says that for consumer reports type of short term mindset of service costs. Lifetime is 100k miles. Then you can change transmission. haha

If transmission needs to be removed to open up ATF cooler lines to radiator that is nuts. There is literally a simple threaded fitting below the radiator. Perhaps there is no breather for excess air that gets in? Even at that, it won't be hard to prevent air ingress if I only crack the return line and prevent the side going to transmission from draining. I don't know man, it seems so easy and is a way to get all the fluid changed. The real problem is I only ordered 5L of oil and want to do it this weekend.

[djn876]

Audi says that for consumer reports type of short term mindset of service costs. Lifetime is 100k miles. Then you can change transmission. haha

If transmission needs to be removed to open up ATF cooler lines to radiator that is nuts. There is literally a simple threaded fitting below the radiator. Perhaps there is no breather for excess air that gets in? Even at that, it won't be hard to prevent air ingress if I only crack the return line and prevent the side going to transmission from draining. I don't know man, it seems so easy and is a way to get all the fluid changed. The real problem is I only ordered 5L of oil and want to do it this weekend.

Maybe to the rad is easier, I've never really looked, and the reference in the manual is probably for the trans connections. Also the lifetime statement isn't really accurate, the maintenance intervals go all the way to 155,000 and no mention of changing fluid other than for the stronic, or hybrid. They are just wrong and that at point changing the fluid would be I'll advised anyway.

I'm just trying to point out it doesn't matter if you get all 9 liters out, but if you want to take the the time and go after it then have at it and let us know how it goes, just seems like a lot of unnecessary risk for no real benefit, it will mix too, so probably need more than 9 liters and this crap isnt cheap.

Sent from my SM-G988U using Audizine Forum mobile app

[sQ5inSD]

at least you are discussing the issue - think of all the clueless owners out there who NEVER even bother to deal with changing theirs!

[wilmar13]

Maybe to the rad is easier, I've never really looked, and the reference in the manual is probably for the trans connections. Also the lifetime statement isn't really accurate, the maintenance intervals go all the way to 155,000 and no mention of changing fluid other than for the stronic, or hybrid. They are just wrong and that at point changing the fluid would be I'll advised anyway.

I'm just trying to point out it doesn't matter if you get all 9 liters out, but if you want to take the the time and go after it then have at it and let us know how it goes, just seems like a lot of unnecessary risk for no real benefit, it will mix too, so probably need more than 9 liters and this crap isnt cheap.

Sent from my SM-G988U using Audizine Forum mobile app

I actually found another forum member in the B8 A4 section mention doing what I was hypothesizing, so that's probably a good way to change all the fluid at once... however also in that thread was mention of how its bad to change fluid if you have pushed it too far, and I do think there is something to when a lot of the clutch material is floating in the fluid, and you change to fresh, it can cause more problems. I had that experience 10yrs ago with my girlfreinds Jeep Grand Cherokee and had to swap her transmission not long after I changed the fluid and filter for the first time and it was overdo. So since I only ordered 5L, I will just do the normal way and change the filter and half the fluid. Then next time, assuming all is good, in 40k mi try to change all fluid and not drop pan or change filter, by purging out the cooler return line while filling transmission in tandem.
https://www.audizine.com/forum/showt...e-fluid/page22

I always planned to change transmission fluid around 70-80k mi, but then life got in the way, a move across country, didn't have a garage for a while and now well its at 101k mi. Hopefully I am doing more good than harm by finally changing it. Worst case I would hope that you can get the 8HP55 rebuilt for reasonable money as the basic 8HP is in all kinds of stuff and there should be a bit of knowledge about it for auto trans specialists.

[djn876]

Yeah as long as it hasnt been driven hard you could probably change without issue, but doing a partial change would probably be better initially as you mentioned to avoid releasing too much varnish or suspended solids clogging things up.

Also note that the cooler valve only opens up above a certain trans temp, I'm not sure where that is, but it won't be flowing constantly.

EDIT: The thermostat for the ATF cooler opens at 75C. Getting it there and keeping it there is harder than it seems.

Sent from my SM-G988U using Audizine Forum mobile app
Attachment 224044

[wilmar13]

Yeah as long as it hasnt been driven hard you could probably change without issue, but doing a partial change would probably be better initially as you mentioned to avoid releasing too much varnish or suspended solids clogging things up.

Also note that the cooler valve only opens up above a certain trans temp, I'm not sure where that is, but it won't be flowing constantly.

EDIT: The thermostat for the ATF cooler opens at 75C. Getting it there and keeping it there is harder than it seems.

Sent from my SM-G988U using Audizine Forum mobile app
Attachment 224044

Good point. I was thinking about that as I drifted off last night. No I'm not thinking about this too much. haha

[djn876]

Good point. I was thinking about that as I drifted off last night. No I'm not thinking about this too much. haha

Lol, when you think you are done and you wake up and realized you dreamed it, THEN you as re thinking too much about it.

Sent from my SM-G988U using Audizine Forum mobile app

[wilmar13]

Also note that the cooler valve only opens up above a certain trans temp, I'm not sure where that is, but it won't be flowing constantly.

EDIT: The thermostat for the ATF cooler opens at 75C. Getting it there and keeping it there is harder than it seems.

FWIW while waiting for transmission fluid to cool down while finalizing fill, I was playing with VCDS settings trying to understand adaptation values, I saw there was a value for transmission cooler valve. At ATF temp of 38deg and coolant temp of 68deg, with ignition on and engine off, the transmission cooler valve was open. I never got it above 54deg when I was trying to fill first time. It has been sitting since. I don't know if that's referencing the only thermostat for transmission fluid to cooler, but I may try it next time.

[djn876]

According to the factory info, it is a wax thermostat, so it's not electronically controlled not does it have a sensor for the status. Maybe there is something else internal to the trans?

ZF is actually very responsive to customer service inquiries, could touch base with them about everything and just see what they have to say.

Sent from my SM-G988U using Audizine Forum mobile app

[wilmar13]

Yeah I have no idea what it was actually referencing. I am a noob when it comes to VAG Com stuff, especially related to transmission. The only way it makes sense to have the transmission fluid go to cooler at all times is if it runs through radiator and coolant is up to temp which it does (maybe the 70 deg ref is for the radiator and my coolant probably did go over 70deg when the ATF was 54 Celcius), but who knows, you know like it may actually be used to warm up the ATF fluid under conditions I was doing (40F deg out, idling in garage) At this point its just intellectual curiosity. I'm all cleaned up and don't want to mess with stinky gear oil or ATF fluid again for a long time if possible. haha

I may send ZF an email just to clarify what is going on from their end.

[djn876]

The ATF temp sensor is built into the trans itself, it is part of the mechatronics unit and submerged in the ATF fluid in the pan and is an integral part of the wiring harness. I posted the picture above as well which shows the thermostat operation, it always has a small amount of bypass flow not going to the cooler so that the wax element will change state, and allow flow to the cooler itself when temp reaches the nominal temperature stated.

Again, I'm not sure where all of the VCDS values pull from, though I have seen some values for "trans temp" actually pull coolant temp though. If you need to, the best way to warm the trans up is with the car in drive, hold the foot on the brake. This slips the torque converter and adds a fair amount of heat into the fluid. It'll warm up when idling too, just not as fast. If you wanted, you can left-foot brake and right foot add a little gas, gets to temp in no time.

And yeah, gear oil smells horrible, and the ATF was an interesting smell too. Neither one was all that pleasant.

[wilmar13]

I don't see a picture... but I can hunt for one when I have the ambition, I have several technical documents on ZF8hp I can look through. I'm focused on other stuff, though I will come back to it as I am interested in learning more about the adaptation values (analysis blocks 2-21) that were there before resetting them. According to ZF they give insight into the condition of the transmission just with the pressure and time it takes to actuate each gear change. Automatic transmissions are very complicated compared to manual and even dual clutch automated transmissions. Getting into stuff like this is kind of fun as you learn how little you know about what you thought you understood, while at the same time increasing your understanding. Its a good lesson that cascades through every aspect of life. If you think you know something, you will never know more... until you try to apply what you think you know and discover how little that is.

OMG, I laid cardboard down, tried to wipe everything down, cleaned out all catch pans and beakers I used, threw all rags, towels and bottles away and took trash outside, yet 24hrs later the garage still reeks of ATF and gear oil. I feel like all my tools are contaminated just because I touched them after only wiping off my hands instead of getting new gloves every time I got oil on them. It comes with the territory I guess. Unless you treat ATF and gear oil as a dangerous contagious pathogen, you and your garage will become infected. You have been warned DIY'ers. haha