Wondering if using a semi synthetic or a full synthetic will hurt my Automatic trans on my 1985 244DL wagon..The trans is working real good no problems..I was thinking maybe some longer life or smoother operation..Trying to figure if I should continue to use the regular fluid when flushing or step up to better oil. I normally flush every year or two..

One of the few areas of the FAQ I disagree with is the tranny flush portion which omits cleaning the screen as unnecessary. I did the flush per the FAQ on my 940 with synthetic, and started to experience a howl at start up, which the shop said was because the screen had become clogged after my flush. They cleaned it out, and it was better, but the tranny failed maybe a year after.

Good information well noted..:)..

Mobile 1 full synthetic atf. Really nice difference. Do you flush by removing the transmission cooler line? Somewhere around $100 + dollars to do. Best to remove the pan and clean it along with a new gasket and screen. Mobile 1 helped my high mileage trans. that was neglected. Bet it would really be nice in a well maintained transmission.

US Diver probably had a really dirty transmission. Best way to do those is to just empty the pan (only) of transmission fluid, fill back up and run 300 miles. Then do the same two more times. A total of 900 miles. This method captures dirt particle suspended in the new detergent and most get dumped with the few quart changed each time. After 900 miles, do a full change Via transmission line along with the gasket and screen. I would think since you have changed your trans. fluid every year, you should look very clean. When I did my transmission I made the mistake of a complete flush on a Non Maintained trans. Had to clean the screen three times, but I was using cheap brand trans. fluid so I could get the dirt out without the very expensive fluid. After feeling good about the fluid looking clean finally, I did another full flush / change with Mobile 1 and a screen and gasket. The Mobile 1 made a world of difference. 240.000 mile on the old trans. And No . the Mobile one didn't cause any leaks.

Yes, I take the top trans cooling line off the radiator and run a hose down to a gallon jug and flush 2 gallons of fresh Dex/Merc through the system. I appreciate your response and glad to hear of your good luck with it..Has anyone had any (negative) problems changing over to synthetics...???

A common issue with a switch to synthetics is for leaks to show up -- and not directly after the switch, but a few months later. The culprit seems to be the better detergent packages in synth cleaning up tiny openings in seals, gaskets that are "plugged" with sludge right now. The detergents clean them up over time and, presto, now you have a tiny leak passage.

If you've been flushing every few years you are LIGHT YEARS ahead of what most auto trannies see. I'd keep doing exactly what you've been doing. It's going to last a long time with regularly changed fluid.
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82 242-6.2L; '17 Mazda3; '16 Crosstrek

Thank you for your response..I flush every year or two..Most of the time every year..The trans in the car currently is a used replacement and it works really good..The first trans started shifting really hard between 1st and 2nd gear..So hard I thought it would break something..So at about 350,000 I had a good used trans put in..I bought this Old brick from a family and their teen was driving it..No telling what he put it through..He must have been hard on it because all the motor mounts were broken and the motor was sitting on the sub frame..I would love to convert this trans over to synthetic but I have to agree using what it was designed to run on...At least for now I will continue to use dino Dex/Merc. Thanks for everyone's input..