[2000lincolnv8]

I have not yet taken the car in to the mechanic to pull the codes since I wanted to figure out the exact symptoms first. The issue is that the car is not shifting gears at around 40MPH or so. I know that the car has a 5 speed auto, any idea where the gear shifts usually take place. Can't tell if it is getting stuck in 2nd or 3rd. RPM's are going up to around 3500 at 45MPH when they used to shift and come back down around then. If I hit the gas when I'm going 40 the car is barely responsive except for a spike in the RPM's but the E code is not coming back. Any input????