Issues with transmission on my friend's 91 ex.

When the vehicle is put into drive, it accelerates extremely slowly, feels like 3rd or 4th gear. When i finally got it up to 70mph it was hitting the same rpms as it would in 4th gear. The sport mode light on the dash stays on, despite the fact that sport mode is most definitely off.

Gonna try tranny fluid flush/filter change, see what happens.

The car came without the owner's manual, how much tranny fluid does this car's tranny take?

Thx for all help in advance.