I also do the seafoam and techron treatments. An oil catch can will help also.

 

sounds like you're losing line pressure inside the trans. maybe a problem with the pump or valve body.

 

With that info, it certainly does sound tranny related.

 

Take it to a shop and ask them to diagnose it. Unless you're a tranny mechanic you can't fix it if it is a tranny issue. Personally I have never seen a bad tranny act like that, usually they slip all the time, or they don't. The possibility on it being tranny related could be an issue with the torque converter. Sometimes they can act like that.

 

your fluid could be low and thats not good for the auto trans. There is not dipstick so you gotta follow the owners manual on how to check it or take it to a shop. Dont wait to do this, low fluid can ruin a transmission.

 

Something to consider with these "sealed" transmissions. Ford recommend a complete fluid flush ever 30K mile. I doubt most people do that including the previous owner of your car OP.

From personal experience, the tranny flush makes a huge difference with these cars. I started to get some harsh shifting a few thousand miles ago (55k ish and also before the first flush around 28K) I had the fluid replaced around 30K and had it replaced a couple of weeks ago. Both times the tranny worked fine for another couple years and almost 30 K miles.

BTW high heat is an enemy of tranny fluid. Above 175F it starts to lose its lube properties exponentially so your weird shifting pattern is about right (60K vs my 30K experience with much higher operating temps being that I'm in AZ).