I am having a problem with my 99 F-150 with a 4r70 and a 5.4. When cruising at highway speeds in OD at about 70 mph when I let off the gas there seems to be alot of drag on the motor ( you can see the RPMs drop real fast). I believe the torque converter is staying locked up and I know its not normal because it doesn't always do it.

Should the torque converter be locked in OD at about 1500-2000 RPMs?

I hope Ford will fix it because this is the second transmission and it only has like 2000 miles on it.

Thanks
Mike