Cruising RPMs?

Could someone please tell me what the RPM should be for a 1980 300SD at 70 mph? I am getting about 3100 rpm, which seems high for a deisel. Thank You.

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That is exactly what it should be.
205/70 tire rotation at 70 MPH is about 950 RPM x 3.07 (rear axle ratio) is 2,915, add 3% for torque converter loss and the engine is spinning at 3,000.
195/70 tires are smaller and rotate faster.
I run 205/70 on my '80 300SD and it handles well.
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I'm right at 3100 @ 70 MPH with my 85 300SD also, provided I'm running on level ground. It drops to 3000 down a 3-4% grade, which would seem about right.
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My 1999 E220 CDI is at 2200 rpm's at that speed
Steinar
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