I promised some photos so here they are:
First, some pretty little hedgehogs!
https://photos.app.goo.gl/2WwNu5LAM87V23y67 (Photo inverted to show similarity)
I used hot nichrome wires to cut through (most of) the filter spigot - to preserve the evidence as much as possible. Turned out to be by far the most difficult part of the job, due to the brass insert around the back (and maybe the bolt, which I left in to stabilise the operation). Broke 4 wires but got through about 90%, then snapped off the last bit.
Filtran OEM Info:
https://photos.app.goo.gl/svjGW92phSpaca5F9
Opened up:
https://photos.app.goo.gl/aeZPmrwUwZFJKq6t9 The oversize gap on the left side allows fluid coming through the lower section of membrane to flow around to the outlet, to the pump.
A tell-tale bulge, not what I expected, but has the same effect of letting dirt, filings and plastic through into the control valves etc:
https://photos.app.goo.gl/YeyCmenYoktkgmA6A
In case you missed it:
https://photos.app.goo.gl/dKpscd5FuGi5Xbp76
A close up:
https://photos.app.goo.gl/t8TwBhfwuhugZ4N88
The most important details about this:
1. The failure occurred at 135,300km. Very early, compared with many, but probably just a result of being driven very hard, and maybe partly due to extra wear from the sudden stalling and cutting out problems described previously.
2. Even more significant, IMHO! The failure occurred very soon after performing a Shift Fork Learn. Like, about two days, maybe less than 50km, came on quickly, and rapidly lead to "TFL*" and DTCs, only 2nd & Reverse gears, very rough clutch operation and Limp mode, with an idle speed increase to about 1,000RPM.
I want to say more about this.
I've read all over the Internet people reporting Power Shift transmission failures very soon after a Ford Service involving Transmission Fluid replacement.
There is no obvious reason for this to be the case, but here's my theory...
As Ford has the equipment and the knowledge, I believe that after correctly replacing the fluid and hopefully the secondary filter, Ford Service then frequently runs a Clutch Learn and maybe even a Shift Fork Learn. Then a quick test drive before returning the car to its hapless, soon to be poorer owner. Huh? They set a ticking time bomb with a very short fuse? How? Did Ford do a very risky transmission flush as well? I say No, not at all.
Clearly, these Primary Transmission Fluid Filters were never intended to be replaced prior to a full teardown / overhaul. This could have been deliberate, built-in, designed to fail obsolescence, or it could just have been wishful thinking.
The fact is, these filters are put there for a purpose - to filter out any contaminants that get into the trans fluid during normal operation, to stop them getting into the Valve Body. This includes wear metals, clutch friction material and of course, those dreaded plastic bits from the disintegrating clutch damper spring separators.
So, normally these wear materials are trapped by the filter, slowly building up with milage and kW.hours. At some point, the filter becomes "significantly clogged", and as a result, increased suction is required to drag the fluid through the clogged membrane.
As you'll see in the photos, there is clear evidence of this increased pump intake suction in the subject filter. You can clearly see how the membrane has been sucked hard against the ribs in the upper filter housing, and stretched into the spaces between them.
https://photos.app.goo.gl/sicd3LX28wSTVnxYA
(For those who haven't seen one, the membrane in a new primary filter is perfectly flat, as seen through the intake hole underneath.) Although at only 135,000km, this filter was already significantly clogged. Then, at some point shortly before the transmission control failure occurred, the suction became too much, and a section of membrane pulled out of the edge seam, as per the photos. And crud then sailed on through into the control valves, causing one of them to jam.
So, why did this happen soon after a service and brand new, fresh, clean transmission fluid?
My theory:
Driving these cars moderately for a few thousand km (in Drive mode), I note that it is rare for the engine RPM to much exceed 2,500r/min. Only if I push it do the revs approach 3,000.
Here, we need to understand a bit about the transmission's internals. Fed directly by the Primary Transmission Filter is a Hydraulic Gear Pump. This pump is gear driven by gears directly off the main input shaft, which turns at Engine speed. FWIW, the gear ratio is about 1:1 (not sure exact numbers, but about 100 teeth on each gear).
Ignoring various losses for this discussion, the ideal flow through this pump will be in direct proportion to RPM. So, let's say the pump delivers 10 litres/minute at 1,000 RPM. At 2,000, that will be 20 l/min, at 3,000, 30.
The pressure drop across the intake filter will form an exponential curve versus the flow rate of fluid through it. For example:
https://www.youtube.com/watch?v=ChkwzU-nH3c
With a new, clean filter, the pressure drop might be just 5kPa at 1,000RPM and 10 l/min and say 25kPA at 4,000 RPM with 40 l/min. However, when clogged, these pressure drop figures will be greatly increased.
With a clogged filter, we might see, for example, 15kPA at 1,000RPM, maybe 40kPa at 2,500RPM and 80kPa at 4,000 RPM. Now lets assume for the sake of this example, that the filter in question fails at 70kPa pressure drop. This is likely to occur at around 3,500RPM.
Now, is the theory becoming clearer?
As the milage increases, so does the amount of crud clogging the Sump Filter. The RPM Pressure Drop will be increasing, but if your engine never Revs over 2,750 RPM, the filter might survive until 250 or 300,000km.
But, at 240,000km, you take it to the Ford Dealer for its regular service, and they change the trans fluid etc, but the old, nearly clogged Primary Filter stays.
Now, being thorough, they also hook up their OBD Unit and run a Clutch Learn then a Shift Fork Learn...
When I ran my Clutch Learn, the RPM never exceeded 3,000RPM. And my filter apparently survived. However, when I ran the Shift Fork Learn a week or so later, I noticed that during the Initialisation phase, the Engine RPM went to 3,600 before settling at 3,000. I didn't think too much about it, and figured maybe I hadn't played my part correctly. But maybe that's not uncommon. Or, maybe 3,000RPM is just survivable by a badly clogged filter.
But at 3,500, it fails, and pulls a seam. You get the rest...
This is my theory for how the dirt, filings and plastic bits suddenly get into the mechatronic unit typically after reaching 150-300,000km. The filter has clogged and suddenly fails, probably at a time of high engine RPM. But it may take a while for a valve to jam, so you probably won't connect the two - especially if the high RPM occurred in the Ford workshop, without your knowledge.
MY ADVICE!
Based on my own experience, I would recommend anyone with a Power Shift transmission to get the Primary Trans Fluid filter replaced every 120,000km to be on the safe side, especially if your car has an unknown history, or gets to work hard.
If you know your car's history and have always diven it kindly, 180,000km is probably okay. Over 200,000km and you might be pushing your luck. Just like the cambelt.
If I get more time, I'll do a write up on what I found to be quite an easy job, though I was very nervous the first time.And as confirmed by AlanM and maybe a few others including now, myself, heating and compressing the plastic filter housing seems safe enough...
Let's keep our PowerShifts running for another 200,000km!
Lastly, a little puzzle for everyone.
What is this?
https://photos.app.goo.gl/uhcSXAyiLGawQCRx6
*The dreaded "Transmission function limited" display message, for those wondering.