There was also a four speed auto called the 4R70W available in that year. If it has a square pan with two rear corners cut off, it is the 4R70W. If it has a rectangular pan with a square cut out of one corner, it is an E4OD. It sounds as if it is starting in 2nd gear. when moving does it shift into any other gears? Does it seem as if the trans is slipping? What is the fluid condition and level? Did you get any codes out of the computer(PCM)? What engine do you have?

If it is an E4OD, there is a very common problem with the MLP/TR sensor on the drivers side of the trans. It gets moisture in side the connector and can cause all kinds of problems and no codes like the one you partly described. Pull the connector and see if there is moisture in it, if so it willl need replaced.