I have a 420sel and would like to change the fluid and filter, first question is what fluid should I use going back in and how much, the second is do I flush the converter and how do I go about this. I have not done this be fore andthank you all for info on the proper method.

You could run some searches on this site to find everything you need for your 722.351 trans aka 722.3. Think clean when doing this job and let no contaminants in the transmission. This is what I recommend including finding and reading more threads on this site.

I used 7 quarts of plain ole Valvoline Dex/Merc which is specified for Dex III Mercon fluid: Valvoline.com > Products > Automatic Transmission Products > Automatic Transmission Fluid > Valvoline® DEX/MERC ATF

After draining and changing filter, trans gasket and new drain plugs(torqued - not that much - find your specs) and washers add 4 quarts. Start engine and add the remainder while checking the dipstick several times, do not overfill or go past top line on stick. You may want to drive it around the block or move through all the gears but only after you see the fluid at least half way between min and max on the stick; then fill it to the max while at operating temp.

With pan out clean it spotless with lint free cloths and replace/place magnet. You may want to open drains for a few hours before dropping pan, and there is a good bit of fluid when the filter is dropped too.

You can turn the torque converter with something like this or a screwdriver or something: Clockwise when standing in front of engine - same way the belt turns.

I got the fluid at Walmart and took them the old stuff to dispose of. If you feel like it you could save some of the old fluid and send it for a report.

so then you do drain the converter too ? do you have to pressure fluid threw the converter or just let it drain and refill the trans ? and thank you for your responce to my questions.

no pressure, just drain. Make sure you get the crush washer for the torque converter plug.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

I thank you both for your reply to my questions Have a great Xmass