Ok well since they go hand in hand, and the problem starts with a late shift, I'd say it's safe to say the late shifting should be looked into first. Sometimes it's caused by a bad throttle position sensor. It relies off the TPS to know how much gas you're giving it, and to shift accordingly. It it's giving a false reading once in a while it can easily cause this. Of course there could a number of other causes but this is definitely the cheapest place to start. I'm not an expert with transmissions, but there are a few guys on this forum who know their way around 4t65e's real well. With the info you provided they may have better advice on this problem. I'm sure they'll be stopping by soon.
