I too have had good experiences with RedLine MTL, and just changed the fluid on my daughter's 1986 190E 2.3-16, my younger son's (same car, but a Euro model) and my wife's 1988 300E with a 5 speed. The point made about having a pump to get the new lubricant into the drained transmission is a must. Once you get a suitable pump, when you do the job you need a 14 mm Allen wrench. I use a mallet to tap, sometimes pretty hard, to knock the plugs loose. Always loosen the fill plug on the passenger side of the transmission first. If you drain the fluid out and have no way to get the new stuff in, you are stuck.

I believe the transmission has an aluminum washer under the plug flanged rim. Make sure you recover it, as when the plug comes out, it can stick to the transmission and then later in the draining process get washed away. Or, buy two new ones.

The differential is the same kind of procedure. I use RedLine Shock Proof differential fluid. Seems to effectively quiet noisy rear end meshing noises and bearing noises. The plugs in the rear end are also 14 mm Allen wrench events, but only one has the Aluminum washer.

Same deal, loosen the fill line first. Don't get hung up on the fluid selection (brand, type, etc). There are many threads on the subject and for the most part, a good modern synthetic will do well in each case. The duty is different though and so rear end juice is not going to work in the tranny and tranny juice is not good for differentials. Good luck, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)