I still use RedLine without any issues. They make a new MTF and an automatic transmission fluid that they recommend for manuals in colder climates.

Fluids can prevent wear, but there is not much a lubricant can do to fix a worn part. I have noticed that each of my cars has a pace that it works best at - shift too slowly and the first to second exchange can crunch, shift too fast and the reaction is similar. It takes some getting used to as I switch from 240D to 300E to 190E 2.3-16.

The 16 valve has the most miles on it, nearing 315,000, and it shifts like butter all the time but I have attended to the shift mechanisms several times - from cleaning and lubricating the shift lever mechanism to changing the bushings on the rods. Since neither the 240D nor the 300E is all that sporty, I adapt to the mechanism's pace or try to. They both have well in excess of 200k miles.

You might want to examine your bushings in the shifting mechanism attached to the shift lever and the transmission. They have a rubber element that can get sloppy and the crunch is from trying to engage a mesh before the other one has actually been bumped all the way into to neutral.

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)