2004 BMW 325 Odd shuddering at highway speed

Transmission problem
2004 BMW 325 6 cyl Two Wheel Drive Automatic 70k miles

A few weeks ago I noticed that when driving at highway speeds that my car would shudder. This happens only in fifth gear at about 65-75mph and only when I give it some gas but not enough to initiate a kickdown to fourth gear. It feels as if there is someone behind my car rocking it back and forth. It accelerates but it is not smooth.

The dealer told me it was the torque converter and transmission. They replaced both under warranty. The problem persists. I also want to add that during all of this, my rpm needle is moving smoothly. Furthermore, all maintenance is up to date and I have no check engine codes.