Vacuum removal of transmission fluid

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I am wanting to change some of the fluid in my 96 grand marquis. thinking of using my vacuum oil pump to remove as much as I can then replace with that same amount and check the level. Transmission is shifting funny after it heats up for about 30 minutes highway speed on really hot days. Hoping replacing some of the fluid will make it stop. Any reasons I should not do this?

Also is Mercon V the correct fluid? Not really finding it anywhere.
 
Have you looked for a drain plug?

A cooler line ATF exchange is a better way to go if you want a complete ATF exchange.

Doing what you mention is good to refresh the ATF. You need a total exchange of the ATF.
 
Do it. I even use a vacuum pump before I do a pan drop to make the process cleaner. I used to do oil changes with a vacuum pump when I had a car with messed up drain plug threads.

If you're going to keep the car for a while, I recommend replacing the filter at least and maybe installing an aftermarket pan with a drain plug.
 
Probably the best thing to do would be a pan drop and replace the filter. It the trans still slips go from there.
 
Gotsta get at the in pan filter, in my opinion. The appearance of the bottom of the pan can help one decide whether to spend any money on the AT.

I recently dropped my pan, added a fram XG16 on an external mount, and have filled it with nearly 7 quarts of the 12 qt capacity. There was noticable shift quality difference being firmer and faster. I had no slipping, just a seeping steel cooler line I had to replace anyway which forced the other procedures.

I have a drain plug, and will likely wait for a deal on ATF+4 and then let it drain overnight and replace with the same amount.

First time I got it on the highway for a bit, and pulled off to check, i found the level low. No leaks, Took highway driving to purge all the air I guess. Carry extra after refilling.
 
More than likely your 1996 was originally specced for Mercon. Since 2001 Ford has back specced everything to Mercon V (ie their spec chart). Only difference is that Mercon is semi-synthetic, shears half as fast as Mercon, and will last longer between OCI's. Since the cost of the 2 is not very different, I'd just go with the Mercon V SuperTech at $4.29/qt.
 
Like stated, you need to change out the filter too. Sucking 4 or 5 quarts out likely won't do anything. You can do a fluid siphon later after the filter change. I believe that transmission has a drain plug for the converter where you can get all 12 quarts out of the transmission. You might want to check on that. Fill up with mercon V.
 
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Originally Posted By: barkingspider
I would do a filter replace and drain n fill at the least.
Yah that is what I did to a 727 in my first Grand Wagoneer. A pan drop,new flocked filter, gasket and 3-4 qts of Dextron. A hail Mary advised by my BIL. I limped home in dribs and drabs, taking 40 minutes to go 4 miles. The filter was plugged and not letting any ATF to pump. The fluid was dark and the pan was full of sludge. After a cleaning of the pan and a refill, it ran like new when I test drove it.
 
I disagree with almost all of the above posts depending on how much effort you are able to SAFELY provide. Dropping the pan requires certain tools (jack and jackstands) to do it safely while using a vacuum pump can be performed under the hood. It all depends on your own circumstances and skill level.

A Ford ATF filter is a "lifetime" filter which only captures very large debris, but changing some of the ATF to "fresh" fluid can help your overheating more.

SPK2000:

Your 1998 Mercury Marquis 4.6L 8-cylinder has transmission 4R70W.

If you drop the pan it will drain between 4-5 quarts (assuming you have the correct level now).
You should be able to remove nearly this much with a vacuum pump and it is much easier to use the pump.
You can drive around for a few days and then vacuum out again and add more new ATF and this will give you a good "refresh".



If you perform a complete flush including the Torque Converter, then the total capacity of your transmission is:

Automatic Transmission, Total Fill
4 speed 4R70W..........13.9 quarts


Wal-Mart has a great ATF for $18/gallon (4-qts) called Valvoline Max-Life...it is a full synthetic and it is compatible with your current fluid:

https://www.walmart.com/ip/Valvoline-Max...13=&veh=sem

If you decide to change the Trans Filter then here is a good kit: https://www.summitracing.com/parts/wix-58955
 
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I would also visually inspect the radiator to see if there is debris like insects blocking good air flow.

And I meant 1996 in my above post...although 1998 is the same.
 
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Did the vacuum and got 4 quarts out. Have driven it yet to see if it's improved or not yet. $20 for 5 qts of ST Mercon V at Walmart. Would have liked the Valvoline but the Walmart I went to did not have it. Meijer only had Mobil 1 for more than twice as much. I may get around to a full fluid replacement but wanted to see what this might do. The car is not worth much at this point. It has been sideswiped and backed into the front end. Nearly 180,000 miles now and I paid $3,100 for it 7 years and nearly 100k miles ago. It has been a great car with minimal problems. If it dies I am likely to get another newer one with low miles.
 
At what you got out of it for what you paid that old car owes you nothing. A lot of those 90s Fords had a tiny nylon gear in there that lived to shear. Big expensive tear down to replace a $2 gear. You dodged that bulle anyways.
 
Originally Posted By: spk2000
Did the vacuum and got 4 quarts out. Have driven it yet to see if it's improved or not yet. $20 for 5 qts of ST Mercon V at Walmart. Would have liked the Valvoline but the Walmart I went to did not have it....



You met the OEM spec with the 7.5 cSt Mercon V specced fluid. Nothing wrong with that. The Valvoline Max Life is a low viscosity fluid at 5.9 cSt. I would not run Valvoline ML in a vehicle calling for Mercon V....not as long as there are certified Merc V's out there. Maybe at over 30,000 miles the Valvoline would finally have the higher viscosity due to less shearing. As long as you change your fluid within OEM periodicity, Merc V is the way to go.
 
Lifetime filter, give me a break. Not the typical rock catching screen of the past.
 
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