2006 Mountaineer Transmition Problems

[k9CAB]

I have a 2006 Mercury Mountaineer, when driving between 40 and 50 mph it make a vibration like you are going over rumble strips. If I turn the OD off it doesn’t do this. Any ideas what this could be?

 

[1Aauto]

Is there a check engine light on or anything?

 

[k9CAB]

No Check Engin light or any other lights on. It is also starting to slip between 2nd and 3rd around 45mph.