I think we did, yes.I think we have confused each other regarding the diff.
I though you were talking about the CV joints. Like in this definition:
"What is a Car Differential?
You might be thinking – what is a diff in a car? In simple terms, a diff uses specialised gears that allow two wheels, connected to the same axle, turn at different speeds. When you turn a corner, the outside wheel needs to turn faster than the inside one as it has a greater distance to cover. This is where the differential, or car diff, comes in.
Car diffs have become increasingly complicated over the years, evolving to meet the needs of more powerful and refined vehicles. The three most common types of car diffs are the open, limited slip and torque vectoring differentials."
But if that is what you feel about the gearbox, of course you do as you feel more comfortable about it, and if that is changing the gearbox you do so.
But first, make sure the noise is coming from the gearbox to not have a situation like with the wheels bearings, when you replaced them and still have the noise.
And if the noise is coming from the gearbox, it could be from the central shaft's bearing, not from the diff. And once you take the gearbox down to replace with another, you should know that replacing the bearing inside the gearbox is very easy with the help of Mr Wild's thread: