Welcome - your first post on forum
So what engine rpm did you see last month at 50 mph, vs the 2000 rpm now?
... my '99 A/T 2.5 liter shows 2750 rpms at 65 mph, which is about the same as your 50 mph / rpm ratioat 40 mph, it's at 1500 RPM and at 50 mph it's close to 2000 RPM ... this just started happening.
So what engine rpm did you see last month at 50 mph, vs the 2000 rpm now?