When the engine is cold and is started the idle is smooth.
With a foot on the brake and it is then shifted into Reverse or Drive
there is a hard shaking. After the engine warms up the shaking goes away.
The ambient temp is in the low 50's.

What's going on?

Thanks,
Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end