I want to check oil level in differential on 1990 XJS convertible.

I can't locate a plug. Rear plate is cast aluminum and has the speedometer pick-up mounted on the rear of the cover.

Do you pull the speed sensor and consider it the fill plug to check the level?

 

I remember the fill plug on the RH side, below the centre line, and a "female" type threaded plug.

Not the easiest to see or get to.

I usually remove the lower tin plate, and reach up from there, and clean all the gunk whilst in there.

 

I replaced that female plug with a male plug. It's easier to get a thin open end wrench than a 1/2" drive socket through that narrow access

 

The fill plug is just to the right and below the speedometer pickup on the rear diff cover.

I was able to get a ratchet into the space between the boot floor and the IRS with a short extension and remove the plug. It does take a bit to figure out the best place to put the ratchet.

 

I located the plug and added just over a pint of 80/90 wt gear oil.

Attached are a couple of photos that I took after removing the bottom plate to get clearance.

Thanks to all for their guidance