When I shift into R and D, the car lurches back and forward respectively, like its snapping to attention after a short delay. Is this normal for these cars? Someone told me it is...just want to confirm.

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car