I would suspect your clutch is the issue. I have never seen one of these transmissions just die like that. About the only thing I can imagine that would ruin the transmission is running it without fluid, or with seriously contaminated fluid. Have you checked the level and cleanliness? You need a 14 mm Allen wrench. IF you got through the trouble to check the fluid, go ahead and change it. Change the differential fluid as well. I use stuff from RedLine Oil (www.redlineoil.com
) and have not seen any issues with a transmission or differential on any Benz I have owned yet.
The clutch is a hydraulically actuated unit and it gets its hydraulic fluid from the brake reservoir. If the the cylinder at the pedal is leaking, you will see fluid in the floor area under the mats. If the unit at the clutch is leaking the leakage is not as apparent, unless it leaks in single area while parked. How does the clutch feel? When you depress it what happens?
I have had to drive my 1975 240D without a clutch before, when one of the springs broke. I started the car in neutral, got it nice an warmed up so it was easy to start in gear. Turned it off, put it in first gear, then started it. The transmission should go into second, third and fourth if you take care to synchronise the engine and driven wheels while in neutral between shifts. Just let off the gas slightly while pulling a bit on the lever, and when the dog clutch on the selector is unloaded the lever will move smoothly, no grinding. Do not force anything. Then, put the lever where the next gear is, push lightly and let the rpms drop to about where they would be if the next gear were engaged, and it should slip into gear. Put it in neutral to stop, and shut off and start the process over to get going. You should be able to do this unless the transmission is shot.
Good luck, and I hope this helps. Jim
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
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)