Hello all,
After checking all of the threads on this forum concerning these caps I am sorry to say I still don't have my answer. Like others, I have oil leaking from a broken rubber cap. I ordered some from ebay that said they would fit but they are too small FTC5414G. I have a 1991 Defender 90. I saw something about the number of splines determines the correct part. Which one do I need? Is there a good link to look up parts for this Defender as I just got this imported to the states from the UK. That guy I bought it from is probably still laughing!! It looks like its going to be a project. Thanks in advance for any advice. Cheers!

Your truck should have ten spline shafts, easy enough to count at the drive flange. The caps are larger on the early 90's
On my 1990 90 I have the metal caps from the series Land Rover, tougher.
Rovah farm are parts suppliers in the states and could help.

Buy genuine not britpart, the britpart ones are sub-standard rubber and weep.

The genuine ones are a tight fit, drop them in hot water before fitting and the fit on snug and don’t weep

I have a 1991/2 parts manual - will look up a part number tomorrow for you, PM me to remind me if I don’t lol