Drive Flange worn (5 speed, DG, 86)

[Disco Denbow]

So having just finished restoring and repairing the swing arms, new bearings etc and replacing the drive shafts (old ones were so worn inside the boot at the wheel ends), I have noticed that the drive flange on the off side of the gearbox has some play/movement when turning.
now I don't know how long this has been the case but am looking to see if anyone has any suggestions.
could this be as simple as the circlip has come off the end of the shaft coming out of the gearbox behind the oil seal or is it more likely to be the bearing inside the gearbox, which I guess means gearbox out etc.
Any help, guidance greatly appreciated
 

[Aidan]

offside is the long side of the differential so the spider gear there is pretty well supported in the diff case, it's usually the nearside where small but visible play may be observed. If it isn't causing oil loss through the flange seal it generally isn't an issue though. If it's been like it a while and is leaking then flange seal may want replacing.
One reason maybe the flange has been replaced, maybe because of a cv joint unbolting and damage to the bolt threads and whoever did it put the spring washer in the wrong way because they couldn't figure out how to get the circlip into the groove. If this is the case then it is hard to now get the circlip off. I see this a bit, but not that often, so I guess home repairs rather than gearbox repair shop work.
Only way to find out is remove cv and pop the flange cap out (thin strong screwdriver down the edge of it and pry against the flange should get it out able to reuse) or punch through soft part off centre and pry but destroy the cap and have a new one to fit
When fitting the flange pop the spring washer in with the inner dome (that sits against circlip) outermost (wide end against flange) and use a new circlip, always, just opened enough to just fit on the end of the shaft then tw4t the circlip into place with something like a deep 32mm socket compressing the washer and pushing the circlip down to fit in the groove then double check it is in the groove with pry bar, to fit cap just put a safety pin down the edge as you press it in to allow air out then remove safety pin

[ZsZ]

What kind of movement it has? radial or axial (in-out or sideways)?
In-out can be a failing spring washer or circlip.
On sideways it is worse news. I think Aidan will clarify it, but either the differential case splines or the flange itself can be worn. Or the bearing is worn and has too much play.

E D I T: he already wrote a longer answer

[Disco Denbow]

Hi Both.

Thank you for the very clear answers and guidance.

ZsZ.   Movement is axial, ie, if you grab the driveshaft and push it up and down the flange will move as if it is not sat on the splines correctly.

Aidan.    There is a little oil loss as well.  My plan was to have an investigation, ordering a new seal from BW first OBVs, but will add in a circlip and maybe spring too.  Hopefully, this will solve the issue or at least make clear what the next step is.

I may be back once I have investigated.