To my surprise, the majority of my problem turned out to be ATF & filter. My initial suspicion was the ATF. But according to the service records from the previous owner, the ATF & filter was changed about 30k miles ago. When I got ready to take the filter off, I noticed that the tech etched his name and the date it was installed on the filter. THE DATE WAS DECEMBER 6th 1990. The previous owner paid for ATF service twice since that date at the same import shop ($129 on the 1st date, $141 on the other. The shop's slogan contains "honest" on the receipts). The old fluid was the worst I've ever seen .... slightly red towards the top & a milky brown towards the bottom. After I replaced the fluid & filter, the shift issue seemed to improve the more I drove it (only 20 mi thus far). I'm throwing the records in the trash. I was using them to plan my service intervals.

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1980 Mercedes 240D
1982 Mercedes 300SD
1985 Mercedes 300D
1993 Dodge Cummins Turbo Diesel