The connector is called a Transtorque Bushing , and I didn't know the any manufacturer , but Newmar used them. So I've learned something today.
The threaded nut; right hand end ; must be backed off slightly, it will loosen then it starts to tighten up, then tap the housing; left side ; lightly with a brass hammer, then loosen the nut again till it tightens and re-tap .
The bushing has dual split cones, that force each other onto the shaft and out to the housing, and if you try to back off the nut to much while the cones are jammed together , you can break the internal retainers ( don't ask
) there are specific re-torque specs for installation , 3/4" or 1" shaft , I'll look them up.
EDIT: 3/4" shaft, 125 ft.lbs torque, 1" shaft , 145 ft.lbs
BTW, the gear box mount bracket on the left is factory , the one on the right was added after the left one failed , I've helped with a similar repair .