XK8 Rear Differential Oil Change


This leak has been on my mind for a long time and I finally got around to checking the fluid level.  I had seen several posts on the rear differential failing and I did not want to have that happen.  So this is how I did it.

As you can see my right side of the differential has a slight leak, just enough to raise my concern.  The left side leakage was far less but still visible.

I had read several posts on how to access the differential drain plug.  One was to drill a hole from the trunk and into the rear frame support brace bracket.  I looked at this and elected not to go in that direction.  I did not want to interfere with the stability of the car.  I have enough other problems!

View of the support bracket.

I spent several hours looking at the configuration to see how to access the drain plug.  I found that it was a  ½” drive so I attempted to insert a ½” universal but it was not going to go between the stabilizer bars and the rear differential housing bracket.

So I went to my buddy’s machine shop and had him make an adapter to fit on my 3/8” drive universal making it ½” because it would fit between the braces.  Well it would not work because of the stabilizer bars in the way.  Back to the drawing board.

This is what I came up with.  I purchased a ½” x ½” stock for $8.00 and cut 3 pieces 1”, 1 ¼” and 1 3/8” and found that the 1” worked perfectly.

This was my first attempt but the plug was so tight It twisted so I went to a solid stock.

I spent several minutes installing the stud tool.  I did not get a photo putting it in because it took both hands, one on the top and one on the side to get it in place.

This is a view from the bottom and where I installed my ½” open end wrench to turn it.

As you can see I could have used a longer reach ½” wrench but I could not find one so I put a pipe on it for additional leverage and got it loose.  You will need to alternate the wrench from the bottom to the top to rotate the plug out.  A real PITA but it worked for me.


I used a vacuum pump to get the fluid out and in.  I got this one at NAPA.  Just remember that this fluid is thick and a light duty pump will not work, the differential fluid is thick.  Also, I cleaned the pump before I used it to install the new fluid.  When I filled it I added fluid until it began dripping out and then installed the plug.  It took in a little more than what I took out but that was to be expected because of the leak.

I measured the old fluid to be sure I I had all the fluid I needed and more if needed to fill the differential.

This tool was my life saver because of the awkward position I needed to be in to install that tool. I would drop it a few times and this little magnet would recover it for me so I could do it again.


It took me time to figure out how I was going to do it but once I had all I needed it went well.  Also the oil I used for my car, 1999 XK8, was 75w 140 Synthetic.  I made several attempts to identify what to use with the nomenclature in the spec book with no results so I contacted Jaguar.




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