I have a 1991 tbird sc, it has a 3.8 supercharged v6 with an automatic/overdrive. When i put it in overdrive and go down the road it will either not go into fourth or it will go into fourth and stay in fourth as long as u keep on the gas. If u let out of the gas to coast or slow down it will drop to third immediatly even at higher speeds. The car has had a new tranny put in. It worked fine when i first put it in. Another more weird thing is when it is cooler outside it seams to shift a little more corectly but not completly. Has anyone else experienced anything like this, or has any knowledge of why this happens? Thanks, Cam