Leaking PAS box

I have recently fitted what was supposed to be a leak-free PAS box to my 90. 2 weeks after fitting, the bottom seal let go in a sudden, spectacular fashion and I boiled it down to the box having been kept in storage for quite a while. i replaced the bottom seal and all was fine for a few weeks. The leak is back and it's not just a few drops. I am inclined to blame the bottom seal again (due to possible pitting on the shaft as is usually the case) but I have realised that the leak is probably starting further up since the chassis leg is pretty wet. Are there other seals that are prone to failure?

Pitting can be fixed with a speedi sleeve, works well on worn transfer box output flanges and lasts to.

I fitted a brand new box 1 year 2 months 1500 started leaking at cylinder cover on taking of cover I inspected quad ring with magnifying glass and found little cris cross scratches all round out side edge fitted new seal now perfect

Seems to be the top seal this time dammit. Time to remove the box. Not looking forward to it at all.

you shuld be abel to change oring in place as far as I rember as yoy lift top cover you you losen adjusting nut on top of box and screw it right hand thread asi screws down you can pull cover up enough to bput on new o ring? quad ring?is it a 90 or 110 if its a discovery I don't if you can do this

It's the input seal, i.e. the one that seals the shaft connected to the steering column. It can be done in situ but requires loads of patience (a virtue I'm not very well known to have).

never tried doing this one in situe