With throttle application in that RPM range (1400>1700) the trans torque converter could be in lock up mode in any gear selected , and on light throttle applied set up a driveline " shudder " that could be described as rough engine run.
Have you checked for trans codes or had the engine ECM scanned?
Any history of trans service ?
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.