I have a 2001 Ford Windstar with automatic transmission model no. 4F50N (also known by the older generic model no. AX4N). I'd like to do a total replacement of the transmission fluid myself. I don’t have a fluid flushing system like professionals use for this procedure. There are many methods and opinions about doing this, and every shop I've spoken to tells me something different - one transmission shop owner even told me to never change the transmission fluid! Guess he's looking for future customers! I've removed the pan and filter already. I'm wondering if the following procedure will work to replace the fluid without ending up with an ATF shower under the transmission?

1. Remove pan and filter. Perfectly fit a “fill hose” to the transmission fluid pump suction inlet (the inlet where the transmission fluid filter was removed from).

2. Connect the opposite end of this “fill hose” to the bottom of a bucket holding 14 quarts of new ATF (the approximate transmission fluid capacity). Raise this a few feet above the transmission so there is a slight positive pressure.

3. Disconnect the ATF return line (returning from the radiator cooler) from the transmission and connect it with a hose to an empty "drain bucket”.

4. Start the vehicle and run it until the 14 new quarts have displaced the ATF in the torque converter and other cavities of the transmission (and the fluid pouring into the “drain bucket” is running clean and clear).

That's my theoretical plan. There will be no fluid pan during the exchange because the fill hose will be routed to the pump suction in the area of the sump/pan.

The ultimate question is this - does the transmission have additional internal drains to the sump (pan), or is the only transmission fluid that returns to the pan only coming from the fluid line returning from the cooler?

Any other ideas to get a complete fluid change would be appreciated!

Thanks,

John

 

That will work, if you don't mind about half of the fluid spraying out from everywhere while the pan is off. Each clutch and band dumps to the pan, the whole lube system dumps to the pan, and so does the valve body. It is going to dump several quarts while you're doing this.

Try this method:Changing ATF Fluid in a E4OD and 4R100 transmission .: Articles. It was written for the E4OD/4R100, but can easily be adapted to this trans. I've used this on a Taurus that also has a 4F50N. I disconnected the line from the trans to the top of the radiator cooler.

 

Mark - Thanks for the answer.

Can you tell me which of the two fluid lines on my transmission is the line returning from the radiator cooler? Your instructions are clear for the E40D. The 4F50N has the two lines located at the same location on the transmission, one just a few inches above the other.

A transmission repairman recommended keeping the ATF fluid about 0.5 quarts higher than the high mark on this particular transmission. Do you have any advice on this?

Thanks Again,

John

 

The line that goes to the top of the radiator cooler is the trans output.

If that doesn't get the fluid level into the rotating parts it's fine. If it does get into the rotating parts it will foam and potentially ruin the trans, or if it expels fluid it could burn the Windstar to the ground.

 

Mark - OK, and thanks again.

I'm doing this fluid change because last week during an unusually hot day in stop and go city traffic this transmission started acting up for the first time ever. It has 150,000 miles on it without any previous problems.

When accelerating from each stop it seemed to work fine through first gear. It seemed to shift into second gear fine, but a moment later it would seem to loose this gear for a second before engaging more positively. Each time was a momentary jerk like the clutch of a manual transmission slipping and then engaging very quickly again. The slip duration seemed to be only a second or two maximum.

Coming home in the evening, with outside temperatures significantly cooler, it worked normally again (no slipping between first and second after stops). It's a 60 mile trip, so it was certainly up to operating temperature (but surely cooler than in the middle of the day).

The fluid level was fine, but I noticed it was a little dirty (not the transparent red I'm familiar with). It did not smell like any burning, but didn't smell normal either. Going through my maintenance records I found that I've overlooked this chore for 80,000 miles - bummer!

I was stupid for neglecting the service/maintenance for so long. I'm doing a total fluid replacement now in the hope that running temperatures will be lower and it will continue to operate properly. Can you shed any light on what may be causing the slipping problem we experienced at higher temps? Any future predictions, prognosis, or additional maintenance I should do right now?

Thank You,

John

 

I really don't want to guess. New fluid might help. It certainly won't hurt.

 

Mark,

I'll use some inexpensive Mercon V for a week or so, and then Mobil 1 Synthetic ATF afterwards. I observed that the Mobil 1 really kept my F-250 transmission running cooler when towing.

Do you believe any of the numerous fluid additives that are available are useful?

Thanks for all your expert advice.

John