2002 Windstar with 130k miles - what should I do about the transmission fluid?

[Mr. Guy]

Recently purchased a 2002 Windstar from a friend, with ~130,000 miles on it. It's in overall decent to good condition, but came from a dealership who turned out to be particularly dishonest, and practically nothing is known about its maintenance history.

Since I just pulled out the original spark plugs (which were in as good of condition as you would expect after being subjected to 130k miles), I have the sneaking suspicion that the transmission fluid and filter have never been changed. The fluid is somewhat old/dirty, but doesn't smell or appear burnt. Of course, there's no way to tell the state of the filter from outside.

The transmission itself is functioning fine; it shifts smoothly, TCC and overdrive work perfectly (though I've noticed the TCC is very enthusiastic about lugging the engine at ~30mph and low throttle) and no slippage as far as I can tell...it's a typical slightly-slushy-feeling Ford automatic. This normally leads me to believe that nothing can be harmed by changing the fluid/filter, but then I've also read of old fluid containing clutch material and fine metal particles "holding together" a high-mileage transmission and problems developing from putting clean fluid in.

I know I can't just leave it and "hope for the best" because the filter will eventually clog and cause starvation failure, but what's the best way to proceed? Drop the pan and do a normal half-change and filter replacement, skip that and take it in somewhere for a full flush, something else? Is there anything to watch out for while doing any of the above for this particular transmission?

[kevink1955]

I would go with your plan, drop the pan and change the filter and replace the lost fluid. After a year I would do a cooler line flush using Synthetic Mercon and let it run.

I was having problems with sliping and surging a few years back while away from home on vacation. A cooler line flush in the motel parking lot cured the problem

Whatever you do, do not let anyone do a machine flush of your trans, do it your self via the cooler lines and replace it with synthetic Mercon

My trans is over 170,000 miles and the shop I use for inspection is shocked it is still going given the slip/surge problems I once had

[Mr. Guy]

Hmm...I'll do that then, sounds about the safest course of action. I was contemplating switching to synthetic if a full flush was in order, anyway. Thanks for the reply.

[wiswind]

I would use a synthetic fluid. Mercon/Mercon V fluid.
While there are a LOT of internet stories out there about transmission fluid "flushes".... MOST places use a machine that simply adds NEW fluid at the same rate as the old fluid is pumped out. This is a fluid EXCHANGE and there is nothing wrong with it. The only thing that I would do is to provide my OWN fluid.
I really like Red Line D4 ATF.... However there are a number of other VERY GOOD fluids out there.
If you are doing the fluid exchange yourself, click on the link to my windstar pictures for some pointers. One thing to watch out for is.....when you pull the in-pan filter out....you will most likely need to pull out the gasket which tends to stay stuck in the transmission fluid intake hole. If you don't do this....then your transmission will suck in some air through the less than perfect seal that you get.

Another thing that i did that I recommend is the addition of the Magna Fine inline filter in the fluid line going INTO the transmission from the in-radiator cooler.

You can approach the fluid change 1 of 2 ways.
EASIEST.....drop the pan......carefully measure the amount of fluid that comes out and you will add that SAME amount when you put the pan back on. Change the filter....wipe down the pan and pan magnets and reinstall the pan.....refill with new fluid. After driving a while.......repeat the pan drop and refill.

Another way. Disconnect the transmission cooler line from the transmission IN or from the radiator cooler in (you want the fluid to flow OUT of the hose when you start the engine) and direct the hose into a catch container that can hold a good amount of fluid. Catch ALL the fluid that drains out..........
Start the engine and let it idle......the fluid will be pumped out of the hose.
Idle engine until fluid flow out of the hose SLOWS or puts out bubbles......turn engine OFF.
Then, remove the transmission pan......catching and measuring the fluid that you get out......change filter, wipe down pan and magnet......and reinstall pan.
Then add new transmission fluid in the amount that you measured that came out of the hose AND when you removed the pan.

With the engine at idle....check for leaks and.....check the fluid level (vehicle needs to be on level ground and engine running at idle to check the transmission fluid level).

Even a LITTLE low can cause issues......but don't significantly overfill either.