At 70 mph on the flat with an unloaded car (84 turbo), I was seeing 3200 RPM with the pedal down sustaining the speed. When I lifted up the pedal, the RPM immediately dropped to 3000 before she started to slow down.

Does this seem about right? I can crawl under and get the tranny model if necessary.

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1984 300D Turbo 350K 50K WVO (two tank) "Maeby"

There is some slippage in the torque converter, so the drop is not unusual. The difference between the top speed of a manual and an automatic version of the same MB is 5 km/h, that is about 130 rpm difference for a W123-300 Turbodiesel with 3,07 differential. Transmission must be a 722.315.

If you want a highway cruiser get a 2.88 rear end or move up to a w124.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Sounds right. The torque convertor doesn't have a lockup function, so even at highway speed there is some slippage and a corresponding difference in engine speed between pushing the car and coasting. Nothing to worry about. A 300D in good condition will run 90+ until it runs out of fuel or the driver needs to stop for a bio-break. The first time I drove my (still automatic at the time) '83 cross country, I was running 95 on I-80 in eastern Nevada (and still getting passed) for hours at a time. A swap to a 2.88, or better yet, a five speed manual, will get the highway rpm down some, with the principal benefit of slightly increased fuel economy.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

put large rear tires help too,I'm run 225s

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

You might want to see what the Highest no load speed Your Engine can do.

Make sure Your Oil level is OK and take Your Car for a 5-10 minute ride around Town and when you get back put it in Park with the Parking Brake on and step all the way down on the Pedal and as briefly as possible see what the highest rpm You get is.
For mine I think it is 4500 rpms to 5000 rpms is normal. I can't remember the specific spec. Someone who knows it can post it.

If it is not doing the Minimum rpm check Your Linkages and clean out the Tubing that sends the Boost Pressure to the ADLA and retest.

If still not making the rpms you can adjust the Throttle Stop Screw. Note that this adjustment is also a safety feature to keep You Engine from over speeding and causing damage.

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84 300D, 82 Volvo 244Gl Diesel