So, coming home last night after an hour and half of freeway driving (at 55mph, this is a 240D after all), I was pulling out from the freeway off-ramp in first gear. I got up to about 5mph and was in the middle of the intersection when I heard and felt a big CLUNK, seemingly from the rear. i thought at first someone had rear-ended me, but then I realized that I had NO power at all going to the wheels. With the clutch engaged and the car in any gear I got a kind of growling from underneath the car, again seemingly from the rear. Some kind folks helped me push the car off to the side of the road, and I called AAA for a tow truck. Brought the car home and had them dump it in front of house until I could look at it in daylight.

This morning I blocked the front wheels, and jacked up the rear driver side to look underneath. The half shafts are dry and the boots look intact. No leaks are evident anywhere: up near the transmission it looks dry, nothing from the differential, nothing from the boots. I put the car in gear with the engine off, and I'm able to turn the jacked up wheel with some resistance, almost like a spline is slipping: nub-nub-nub-nub. The other rear wheel is in contact with the ground, so turning the jacked wheel makes the half shaft turn, which goes through the differential and makes the main drive shaft turn. The universal joint in the center turns and the flex disc up at the transmission turns and looks intact. The nub-nub-nub noise is happening up at the transmission end of the driveshaft, but I can't tell if it is in the transmission or if it is in the clutch. With the car out of gear the wheel spins more easily and nothing makes noise, all the shafts turn as before.

Some other facts about what I've observed about the clutch and transmission. The clutch was replaced six years ago and about 25k miles ago when I put in the new engine. It wasn't a genuine Mercedes part, which I now regret. After about a year I would hear a little ringing / scraping noise from what I thought was the clutch, but everything else was OK so I ignored it. I drained and filled the transmission with red ATF during that same time period. Transmission has never popped out of any gears; about the worst thing that ever has happened is it will grind going into second if I don't wait for engine RPM to drop far enough to match the wheel speed.

So, any ideas on how to further diagnose this? Thanks,

Kurt

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- '79 240D - engine swap complete! Engine broken in! 28-31 mpg! Lovin' the ride!
- '86 190D (W201-126) - 2.5 NA engine, 5 speed, cloth interior, manual climate controls, 33-34 mpg (sold to forum member).