P38A About to take out the gearbox out what to look for to do with clunk when reversing?

As in previous post roll pins gone (again in a year).

But whilst taking it all a part what might I look out for in regard to a small but definite clonk when reversing. It happens after selecting reverse and after the clutch has taken up and the car just starts to move? UJ's? Play in prop shaft? All good a year ago. Least of concerns but whilst under there.......

Any suggestions or pointers most welcome.

Thanks, also thanks for anyone who comments on previous post...

Could be UJs. But also there was a service bulletin about play in diff drive flange splines or rear hub to half shaft splines at one time. Bulletin 0001. CDS ref L8431. Issue 2. Date 26/04/2000. See RAVE for details.