Working on a friends 05 taurus, drove fine the day before no problems at all. Then went to use it and the transmission just slips out trying to go 25. Accelerates without issue till about 18, then it struggles a tad to get to 20 and with the pedal floored it slowly makes it up about 22, after that the engine revs free like in neutral. Does this in 1 2 and OD posistion. Car has about 76K miles on it. Has anyone come across an issue like this? Some searching I did said TC was issue.

Edit:
No ODBII codes found but Check transmission light came on, gets reset if car is turned off.
Fluid is proper level and a beautiful red.

 

It sounds like the trans is losing pressure internally. It should be checked for operating pressures and that may help pin down the cause.