Transmission slippage

What is your question?

80000 miles. Car starts moving normally but shifts quickly through the gears bang - bang - bang until trying to shift into overdrive at about 25 mph. It shifts quickly weather I am applying full throttle or taking it easy. It then slips and will simply over rev until it gets to speed which takes a fair amount of time due to the slippage. It doesn't seem to be slipping once to speed but I can't really tell either if it really locks in. However if I apply full throttle at highway speed it does rev up and slip.