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958 Cayenne DIY: Transmission fluid "flush"

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958 Cayenne DIY: Transmission fluid "flush"

 
Old 01-16-2019, 10:58 PM
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twodollardoug
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Default 958 Cayenne DIY: Transmission fluid "flush"

As promised here are the DIY's I promised.

First up is the transmission filter and flush.

The filter change is already documented so I will start at the flush/fill. First I had to get a fluid transfer pump and modify it for our Cayennes. First thing was to make sure it's clean. These tools aren't built in laboratories. Mine had a bunch of plastic shavings in it: It would also be possible to use a hand pumped setup - but more work and not as convenient.




Then I had to figure out how to get the fluid from the container into the trans.

The ball valve came with the tool, but I added the quick disconnect so I could separate them to check when the transmission is full. Then on the end of the hose is the fitting that actually screws into the pan of the transmission.

The fitting is off a 40 IDF Weber carburetor. It is the threaded fuel inlet where fuel enters the carb. 10mm I believe. The Weber fitting temporarily replaces the trans drain plug. (A store bought version of the factory tool can be found by searching Google for "VAS 6262/2 WE 1390" - in this case one was found for less than $8 on eBay.. or Amazon for a bit more.)

The little green riser tube inside the pan stays in place. The green riser tube lets you know when the trans is full. The trans is full when the transmission is at 40 degrees Celsius and fluid stops pouring out of the little green tube.




Detail of the drain plug (from the manual):

Part 1 is the drain plug. Part 2 is the green riser tube.

I filled the trans with 7 quarts of fluid.



I used nitrogen to charge the fluid transfer bottle. I didn't want to introduce unnecessary moisture using regular shop air.



Here is what the setup looks like before the filling starts.



And this is a shot of the filling process. Remember this is all done with cold fluid engine off.





Ok, now the trans has 7 quarts of fuid in it. I added another 5 quarts to the fluid transfer bottle and charged it again with nitrogen.

Now I moved to the front passenger side of the car and found where the two transmission hoses enter the transmission thermostat. Just before the cooler. Super easy access. One bolt holds the tubes into the t-stat. Its a green 10mm headed bolt, you cant miss it. Remove the bolt and wiggle the lines out of the t-stat.



This is a shot of both tubes disconnected. You will need a 3 to 4 gallon bucket under those hoses to pump out the black nasty. I can't remember if the outlet hose is the top or bottom hose. It doesn't matter, point them both into the bucket. (Note - on reassembly it would be best if the two O rings sealing this fitting were replaced.. and the factory torque for the bolt is 1 Nm (0.5 ftlb.)



From the manual:



Now is the time to get your helper.

He/she will be in the drivers seat and will need to be able to hear your commands. We rolled down the windows so we could talk to each other.

While you are at the front of the car holding the hose into the catch bucket have your partner bump the engine. Turn the engine on then immediately shut if off. Only one hose will shoot fluid. And it will only shoot momentarily. Now that you know which hose the fluid will flow from, you are ready to start the operation.

Go to the fluid transfer bottle and open the valve so now fluid is flowing into the trans. Run to the front of the car, grab the hose and have your helper start the engine.

Now you are using the transmission pump to pump out the old black nasty fluid. With the engine running, and foot on the brake, have your helper shift to reverse, hold for 10 seconds, shift to drive, hold for 10 seconds, back to reverse, hold, then park and hold. Throughout this procedure, you are watching the stream of black fluid shoot into the bucket. If at any time you see the fluid stream turn to foam stop the engine immediately and let the fluid transfer bottle catch up. Mine never ran dry. When you see clear crimson red fluid exiting into the catch bucket stop the engine. You have now pumped clean fluid through the entire transmission, valves and torque converter.

Time to regroup.



Now is the time to reconnect the transmission hoses to the t-stat and clean the area up real well. you will want to check for leaks during the next step. (Tightening torque: 1 Nm (0.5 ftlb.)

At this time we don't know the level of fluid in the transmission, so fill your fluid transfer bottle back up, charge with air and fill the trans again. Your engine is still off. After 2 or 3 quarts have been transferred, stop the flow open the quick disconnect and see if the trans is full. If you don't get any backflow out of the trans add more fluid until you do.

The next step will be to top off the trans fluid. This will require a way to get a temperature reading. I thought my Durametric enthusiast would read the transmission temperature but sadly it wouldn't. (not real happy about that one) So i used my hand held IR temp reader. (Note the iCarScan diagnostics tool can read the transmission temperature.)

Next, with the transmission full of fluid have your helper start the engine. Again, ask them to go thru the drill of, foot on the brake shift into reverse for 10 seconds. same routine as when you were pumping out the black nasty. While the trans is coming up to temperature check that your hoses aren't leaking at the t-stat. The t-stat is where I took my temperature reading. I figured the reason for the trans needing to be at 40 degrees Celsius is because that is when the t-stat opens and fluid is running through the cooler. Or maybe because of fluid expansion when at 40 degrees or both. Anyhow, when you get up to temp pull the trans drain plug or your quick disconnect and let the excess fluid drain from the transmission. (Editor - the reason is to account for the fluid expansion when it heats up.. at least that's what the manuals say.)

I don't think there is an exact science to determine when to plug the pan. My fluid went from a steady stream and transitioned to a kind of chugging flow. I plugged the trans when the fluid started chugging and the job was complete.

Note from the on-line AllData manual: (This describes waiting for the thermostat to open up so fluid fills the oil cooler at 100C, then letting it cool down to 35C to check the level. That's probably significant.)

ATF cooler lines were opened.

For example: when replacing the transmission, changing ATF, changing ATF lines, replacing ATF cooler, replacing ATF thermostat.
  • Warm up transmission in lower load range. Switch all transmission ranges several times while doing so.
  • Read out the ATF sump temperature using the PIWIS Tester.
  • The ATF temperature must be 100 ░C (cooling system open).
  • Let ATF cool down to approx. 35 ░C.
  • Selector lever is in position P.
  • Press the brake pedal and shift the gear lever slowly through P-R-N-D three times. Hold the selector lever in each position for 2 seconds.
  • Test and filling procedure at idle speed with air conditioning switched off.
I'm going to add a table of specifications - so they can all be found in one place:

Transmission Oil Cooler connection O-rings: N 906 660 01 O-ring -14 6 11,5 X 3 (2 needed)


The oil drain plug requires a new sealing ring. If reusing the old one - cut those numbers in half (10nm, 7.5ft/lb)

Oil drain plug seal: 958 321 581 00 Sealing ring

Last edited by deilenberger; 01-18-2019 at 01:30 PM.
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