Only way to check is to watch the coupling and box shaft -- if the coupling can rotate slightly before the shaft moves (or you can see the pins moving in relation to the rest of the coupling), it's bad.

If the slop is internal, sway the steering box.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!