I think Barry has a good idea there, the trans on the SD might not be going into high gear. What RPM's do you see in each at 70? 3000 and 4000? Also, it's possible the torque converter on the SD is on the way out. Hope not.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.