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Posted this to see if I get thoughts from forum members with much more technical know how on PDK. Hope get some details here.
Recently did PDK transmission change on the PTT. Before doing so, did research for some time, trying to get some technical details about the process.
Have done this on my CTT as well a couple times. To be honest, many folks in CTT world (non PDK), were doing without PIWIS, and I have not heard of anyone having any issues.
The general process is:
- car up off ground but level
- drain old fluid measuring how much came out
- put in new fluid
- run through gears few times while stationary
- bring transmission to 40 deg. Celsius
- top up until fluid starts leaking out fill/inspection hole
-close off all plugs and put things together. Done.
My curiosity is around how precise does the fill have to be?
Surely, the car cannot tell difference in mL. Putting in 1/4 of a quart too much is 250cc or 250mL (thats one glass).
What is the level of precision needed for these fills? I have been reading that overfilling transmission can lead to issues like over pressurizing system, foaming, etc.
However the more I read, I find contradictions in each point.
For example - foaming.
Foaming can occur if oil is picked up by gears in overfilled transmission. Causes fluid to overheat and lose its lubrication properties. Can help damage transmission.
I found that Pentosine FF3 and other trans. fluids, all have anti foaming agents in them, preventing that exact behavior.
So if fluid has anti foaming, surely small amount of overfill will not be something to lose sleep over, or is it?
Another example, fluid expands as temperature increases.
PDK is to be filled to max at 40C. That is 104 deg. F.
Anyone who has Panamera can tell that the car is hot at run time. Once parked overnight, engine is still at about 85 deg F or 30deg Celsius in the morning.
So if I do PDK change in summer time, and ambient temp is 85F, how much can this fluid expand in 20 deg. F? I am sure it wont be a lot. Read below.
Looking into this further, there are charts showing thermal expansion of petroleum products.
These values are between 0.0007 and 0.001 (this is a coefficient value 1/degree C).
Here is some mathematical stuff:
You cancalculate thermal expansion of liquid by formula: dV = Vo β (t1 - t0)
dV = change of volume
Vo = Original volume (initial volume amount)
β = coefficient of expansion, (m3/m3 oC, ft3/ft3 oF) - sample Chart Here
t1 = final temperature (C or F)
t0 = initial temperature (C or F)
Given above, we know for PDK:
Vo = 8.5 (quarts = 0.284071 cubic feet - used typical change time fill quantity, at volume converted to cubit feet per coefficient of expansion)
β = 0.001 (used worst case or most expanding coefficient - Petroleum...rage is from 0.0007 to 0.001 from chart - using values from the Celsius column since we use temp in that unit too)
t1 = 40 Celsius (temp at time of top PDK up)
t2 = 30 Celsius (cool engine summer time temp)
Mixing all this together, you get result of
0.284071 cu. ft ( (0.001)(40C-30C) ) = (0.284071 cu.ft.) (0.01) = 0.00284071 cu.ft = 0.08499994597403 quart (converting back to US quarts) = about 4cc (one fifth of a 20cc cup of cough medicine)
This cup shows you about 20cc of fluid, so 4cc is way less. Imagine adding that to your FFL3 fluid fill in PDK, sitting already at 8.5 quarts or 8044cc.
So looking at above, if you put in 8.5 quarts of FFL3 fluid into your PDK, while car is at cool temp,
once you heat the PDK to 40C, that 8.5 quarts will expand to be 8.50284071 quarts.
Meaning, the fluid will have expanded by about 0.99% or rounding off, to about 0.1%.
If that is true, then your 8.5quarts added, when heated, will become 8.5028 quarts, which is a minuscule amount of change, equivalent to about one hundredth of a glass, about 2cc worth.
If we assume that PDK transmission fluid expands at twice this rate (say coefficient is not accurate and we want to compensate for its possible error), doubling this bring expansion to about 4cc.
That is still a very small volume, about one fifth of a small cup you take your favorite cough medication with (20cc cup).
All that in mind, I find this very surprising, that PDK transmission would have this level of sensitivity, to be accurate to 2cc difference in expansion.
Is it possible that there is some bs mixed in the PDK fluid change technique, to help the company bottom line in terms of revenue from customers? Dealers charge about 750 from what I remember for doing this. Selling 10k cars brings in $7.5 million dollars revenue after 60k miles (or about 4-5 years, about $1.85 million per year). That would be for USA market only.
I looked up sales numbers for USA market. Took the 2014 model as it is more reflective of those who are more likely to do PDK oil sooner than later.
USA market sold some 4750 cars in 2014. Adding other markets in the World, you are looking well over 10000 units per year.
What am I getting at here? Is it possible PDK transmission fluid tolerance is so precise because of technical reasons that elude me? Do these technical reasons justify fluid volume sensitivity of one fifth of a medicine cup (4cc)? Put that 4 cc in a glass of water. Now picture 8.5 quarts of FFL3 in the transmission. Then add the 4cc to that volume. I bet transmission would not even detect that difference.
Please give me some info if you have it, so I can change my mind on this. I understand overfill/underfill of fluids is an important issue, just trying to justify how the modern PDK in Panamera, would detect 4cc (which is already overinflated number), and cause damage in its parts over time. I can see overfill of quart or 2 quarts can be an issue, but 4cc?
Please give me more insight if you have the details. Chime in with your thoughts. Thank you.
Yes, I agree..can't see how 4 ml or even 40 ml out of 8000 mL (0.5%) would make a difference in terms of the fluid volume. How high is the fill plug on the PDK unit? The only thing I can think off is its not the change in fluid volume that is critical, but what about the remaining air space? An additional 10, 20 mL of air if the volume of air is only 100 - 200mL can be significant maybe?
If you look at video simulations of the PDK transmission, you will see the fluid fills less than half the volume of the chassis. So adding 4cc extra, even 300cc extra would not make a difference.
I am not aware of any sensors that would be affected by this tiny amount of fluid variance.
I am not aware that this tiny amount of fluid could/would increase pressure in fluid at temp/speed.
Look at this PDK video, from ZF, maker of the 2010-2013 PDK for Panamera: VIDEO
Originally Posted by NJS_04_996
Yes, I agree..can't see how 4 ml or even 40 ml out of 8000 mL (0.5%) would make a difference in terms of the fluid volume. How high is the fill plug on the PDK unit? The only thing I can think off is its not the change in fluid volume that is critical, but what about the remaining air space? An additional 10, 20 mL of air if the volume of air is only 100 - 200mL can be significant maybe?
It's a Canadian and Euro thing. There is another video I watched which actually showed levels of the fluid while PDK in motion. The levels shown were less than half.
Cant seem to locate now.
Anyways, I still have not got time to do front final drive oil change, so next time get time to try, I will get the car up and will double check the level of PDK fluid after driving a week or two.
I can tell after change, my shifting and power delivery is smoother, and its not just me. Wife also said it feels smoother. So far I have not observed any issues at all.
Like I stated earlier, 8.5 quarts came out (letting it drip for about 20 minutes), I added 8.8 quarts until it started leaking out the fill hole.
Originally Posted by DogWood
nice video, but I can't take anyone who says 'zed' for 'zee' seriously
Found this to be interesting - might go towards your .3 quart difference
"When is Porsche PDK Transmission Repair Needed?One of the most common sources of major transmission problems is a lack of transmission fluid. It is important to routinely check your fluid levels and replenish them as they get low. If you notice a puddle of fluid under your car, it’s probably leaking. Other common indicators of transmission problems aren’t hard to miss if you’re keeping an eye out:
Illuminated warning lights
Strange smells
Delayed movement
Strange grinding noises
Our service department has the resources and trained technicians to quickly diagnose and repair your vehicle, so you can get back on the road."
Finally found a diagram showing the location of the fill/inspection plug - seems it is only about half way up the body - so I think we can safely rule out the airspace theory :-)
the above quote makes me thinking I will be checking the level sooner than later - but I don't plan on changing the fluid until next year when I'm closer to 60k
If you look at video simulations of the PDK transmission, you will see the fluid fills less than half the volume of the chassis. So adding 4cc extra, even 300cc extra would not make a difference.
I am not aware of any sensors that would be affected by this tiny amount of fluid variance.
I am not aware that this tiny amount of fluid could/would increase pressure in fluid at temp/speed.
Look at this PDK video, from ZF, maker of the 2010-2013 PDK for Panamera: VIDEO
Pretty cool. But this might not be the actual PDK the Panamera uses? The video shows the two chamber PDK similar to what I found for the 911s - which specifies a clutch fluid change at 60K, and transmission gear change at 120K. Wikipedia suggests three ZF 7 speed dual clutch variants used in Porsches: 7DF-45 used in the 911s, Boxsters, and Caymans; 7DF-70 for the higher torque 911 turbo, and 7DF-75 for Panameras and Macans
I have no leaks in the transmissions. Looked all over and everything is bone dry, no dirt/grime/discoloration.
The only time I saw anything was during PPI, there was a little moisture around the drain plug (as if it was loose or seal was giving).
Spoke do PPI shop and they just recommended monitor. Since then (it was all wiped), there was no visible moisture either.
So it is possible was a bit low. I plan to check the level next time I put it up for some TLC.
As to the vid, I remember getting the link from some Panamera site, not sure exactly where but once I got to the ZF, I bookmarked it.
I would def. say, check your level if you do not plan to change. I will do the filter change next iteration, saw several posts up including analysis numbers, and most details were no anywhere near half way with numbers.
Originally Posted by DogWood
Found this to be interesting - might go towards your .3 quart difference...
Just to wrap this up, ZF made one type of transmission for mid/rear engine applications (911, boxter, etc), and a unique transmission just for Panamera.
ZF PDK transmission for 911/boxter/etc, is different. It requires separate fluid for the clutches. Panamera ZF transmission 7DT75, was uniquely made for Panamera, and has one compartment for gearing + clutches (same fluid - Pentosine FFL3), and another compartment for front final drive (Shell TF0951).
I have a thread with all details concerning this topic here.
Hi, couldyou please tell me where the fill hole on Panamera? You've mentioned that you have the diagram, thanks.
Originally Posted by DogWood
Finally found a diagram showing the location of the fill/inspection plug - seems it is only about half way up the body - so I think we can safely rule out the airspace theory :-)
the above quote makes me thinking I will be checking the level sooner than later - but I don't plan on changing the fluid until next year when I'm closer to 60k
07-23-2018, 10:28 PM
PDK transmissions and fluid fill
