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Discussion Starter · #1 ·
2006 vulcan 50k AX4N

I disconnected the return line and ran engine until flowing stopped, per wiki and also the Ford shop manual. Filled to mark. Drove the neighborhood. Rechecked oil level. Car didn't move for about 2 weeks.

2 weeks later, when the car was started, it didn't move backward, "check transmission" on dashboard (where "door ajar" appears), and transmission slip error codes. Added 0.5 qt. Cleared the codes.

Car has been driven good 100 miles since then. No more codes or problems.

Does this method of draining oil cause temporary errors until all corners and crevices get filled with oil? Any other way to explain my experience?

EDIT: Oil was not burnt. Pan dropped and filter replaced.
 

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That about says it all. You ran it dry, which may or may not have hurt anything. This method is to my way of thinking not a safe procedure when the simpler way is to just drop the pan, change the filter, clean the pan and magnet and button it back up. True you only get half the old oil out, but it is the dirtiest part of the fill and you do not risk having the problems you mentioned. This, especially when the transmission only has 50k on it.

The big question is, did you replace the oil with a full synthetic like Mobil One or my favorite Wolf's Head full synthetic extended life transmission oil? Trans oil temperature on a hot summers day will exceed the engine water temp, sometimes going beyond 200 degrees. And, this is where the synthetic oils shine. Even though an add on transmission oil cooler would be advised to keep the temps down below this level.
 

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The flush procedure guarantees 3-4 quarts above sucking in air if done correctly. I would check the fluid level again. 0.5 quart is not the difference between full and not working. More like 2 or 3. If it ran fine for 100 miles it's probably OK. Not much else you can do anyway. Ford recommends keeping the level at the top of the hash marks to prevent sucking in air on turns.
 

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Interested, tell me more !

The big question is, did you replace the oil with a full synthetic like Mobil One or my favorite Wolf's Head full synthetic extended life transmission oil? Trans oil temperature on a hot summers day will exceed the engine water temp, sometimes going beyond 200 degrees. And, this is where the synthetic oils shine. Even though an add on transmission oil cooler would be advised to keep the temps down below this level.
How much does that Wolfs head full synthetic extended life transmission oil cost per quart?

When you run this Wolfs head oil -- How often in miles are you now flushing the transmission oil ?

Are you running a trans. cooler?

Sorry about the questions but I am seriously thinking about doing the above two items on my 04 Sable.

Thank you in advance,

k8crd
another Michigander
 

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You did the changeout incorrectly, you are not supposed to run it dry ever. You pump out a certain amount, then add more, but you don't run it dry. If you run it dry, it will foam up. That will cause false fluid level readings, so you probably under-filled it as a result. Low fluid will cause slipping. Half a quart is a lot low.
 

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Discussion Starter · #6 ·
I have a 2005 Ford Taurus shop manual. It says run the engine until oil flow stops. I trust Ford engineers and technicians. No way this will make the transmission run dry.

I can prove it by numbers. AN4N has about 15 quarts to start with. Run motor and drain 2-3 quarts first. You have 12 quarts still remaining. Drop pan and you lose another 2-3. Now you have about 10 quarts in tranx. Add 10 quarts. Run motor and drain 10 quarts. You have 10 quarts in tranx. This is far from dry.

My question was not if the procedure would damage the transmission, but if anyone experienced a temporary transmission slip.

I will check the fluid level again. Thanks.
 

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After you add the 10 quarts you are supposed to run it again until fluid stops coming out of the cooler hose. Then you put the 5 or so remaining back in. 10 quarts total is dry in the pan-it's all in the torque converter and fluid passages!
 

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Discussion Starter · #8 ·
You are correct. It is dry in the pan and the pump runs dry for a few seconds.
 

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I never ran mine until there was no flow. Just stopped when it slows way down. And I would always run an extra quart or so out. Making sure that all the old stuff was flushed from the tranny.
 

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The approach I always used on my Aerostar was to drop the pan and replace the filter first, then refill with new fluid. Then disconnect the return line and begin draining the old fluid out, adding new fluid as the old drains away. This keeps going until new fluid begins draining out, or until about 12 quarts has drained out. At no point do I ever let the pump run dry. If it runs dry, it will foam, and that will cause a false fluid level reading.

If the fluid level is too low, it will cause slipping.
 

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I have a 2005 Ford Taurus shop manual. It says run the engine until oil flow stops. I trust Ford engineers and technicians. No way this will make the transmission run dry.

I can prove it by numbers. AN4N has about 15 quarts to start with. Run motor and drain 2-3 quarts first. You have 12 quarts still remaining. Drop pan and you lose another 2-3. Now you have about 10 quarts in tranx. Add 10 quarts. Run motor and drain 10 quarts. You have 10 quarts in tranx. This is far from dry.

My question was not if the procedure would damage the transmission, but if anyone experienced a temporary transmission slip.

I will check the fluid level again. Thanks.
:argue:
Do the math: 15-3=12; 12-3=9; 9+10=19; 19-10=9

Capacity 15 minus the 9 left in the trans is 6 quarts low. That, my friend, is a dry transmission and will cause transmission damage, slippage, etc.
 

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The approach I always used on my Aerostar was to drop the pan and replace the filter first, then refill with new fluid. Then disconnect the return line and begin draining the old fluid out, adding new fluid as the old drains away. This keeps going until new fluid begins draining out, or until about 12 quarts has drained out. At no point do I ever let the pump run dry. If it runs dry, it will foam, and that will cause a false fluid level reading.

If the fluid level is too low, it will cause slipping.
Why would you replace the filter before getting all the old fluid out? Sounds counter productive. I get what you were trying to do (not leave the pump cycling air/no fluid...but there has to be a better approach.
 

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If there's no old fluid in the pan, and you discharge the output of the pump to a bucket via the cooler line, very little old fluid will end up back in the pan.
 

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Exactly. You drained all the old fluid out of the pan already, so the only old fluid left is that in the torque converter, valve body, lines, and cooler. If you disconnect the return line, the old fluid in those systems will not re-enter the pan. Some old fluid will remain, but the amounts would be miniscule. Some new fluid will be wasted, it gets mixed with the old in the torque converter. But whichever approach you take, there is no easy way around that. If you drain some old fluid and add a little more, there is far more waste, cause the old and new fluids mix. If you allow the pump to run dry, the pump can be damaged, but the pump will churn the fluid with the air, making a light froth. This froth can get further churned in the torque converter. This froth can take up space, but it is compressible and the air eventually gets out, allowing the fluid to return to its true level. The torque converter can hold about a quart and a half of this froth, maybe more. If you fill the system with this froth in there, the level may look correct, but the air escapes. Soon the level can drop to where the pump may have a difficult time building the proper pressures, and the transmission begins to slip. Restoring the proper fluid level fixes the problem.

Ift is best to take the approach that avoids this approach. I also check the fluid level frequently just after a change, again because it can take a moment for the real fluid level to show.
 

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Ahhh I get it now, yea that actually makes sense. I will definitely keep this approach in mind for the next fluid exchange. Considering the pump is one of the weak points in a 4N/4S, I'm all for keeping wear & tear down on it.
 
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