I rebuilt my sons 46re and replaced the TQ, cooler, Kolene steels, Alto red eagle clutches, new reverse drum, new piston support, new internal electronics, and installed the trans Jr shift kit. Went for a test drive and there's a bad vibration/ shutter between 1500-2000 RPMs. This only occurs when cruising at a steady speed, slight acceleration, and on the highway at 65-75 MPH. It does it whether the OD is on or off, shifts through the gears nicely with on issues. Any ideas?

5.9, I didn't touch the crank sensor. I left it in place when I removed the trans.