Welcome to the forum
I dont think anyone on the forum has managed to split an RX4 propshaft...I had a go at mine, and came to the conclusion (perhaps incorrectly) that it had been friction welded together....Whilst I could have taken it to work and cut it up, I really couldn't be bothered and bought a new OEM unit and fitted it myself to save a bit.
As you've seen, since then, a few members have managed to get them refurbished and this is about half the cost of a new unit.
A couple of members have been able to split and refurbish the Trekka propshaft, have a look at the thread
, it may give you some inspiration, although the Trekka is a little different to the RX4
There have been instances of the rubber coupling between the propshaft and the diff failing....this coupling is available on
I'd get in on a lift with the engine running and in gear to let the wheels spin and trace the noise