The clutch packs in your Powershift transmission are not releasing and engaging the proper time.
There are adjustments that can be made on the transmission control valve on the right side of the
tractor under the cab. However, don't attempt to adjust them until you've read the proper way to
do it. You can seriously damage the transmission with improper adjustments.
If the adjustments on the control valve do not fix the problem you may have to replace the control valve.
Hope this helps,
Mark