Many previous posts indicated difficulty reaching and removing the XK8 differential oil plug. I first positioned front wheel chocks, then jacked up the vehicle from the bottom of the differential, when both rear wheels were about a two inches off the ground the floor jacks were positioned under the rear jack points and the vehicle lowered upon them and gave a good push/shake to the vehicle and all was tight. Get yourself a short 3 inch length 3/8 inch drive "wobble extension" with a 3/8 inch 1/2 inch drive adapter, don't snap the adapter on all the way, just half way allowing for maximum wobble. Insert extension straight at and into the plug and back out with ratchet wrench, took less than 15 seconds to remove differential oil plug. When reinserting plug I had to use my left index finger inserted into the plug and gradually rotate back in, once the threads grab place the wobble extension back into plug and crank tight. Terry's Jaguar sent me Castrol, BOT 720 Gear Oil, I decided to only top off the diff fluid using a cheap Harbor Freight transfer pump (once it starts running out the plug hole it's full) and fully change it in the near future, the diff was over 1/2 quart low. This gear lube diff top off made a noticeable improvement of smoothness in the rear end while the transmission shifts also became smoother and practically unnoticeable. A friend of mine unexpectedly dropped by after I changed the diff fluid and I had him drive the vehicle, he screamed out: "I can't even feel the gear shifts", no joke. On the top right side of the differential is a pressure vent, use a 14mm wrench and remove it, blow it out with compressed air, if it's really clogged blow it out with brake cleaner and then blow compressed air all through it and reinstall it with the 14mm wrench only firm tight, don't gorrilla it.

ER.

 

That's great if you have a coupe ,but there's a bloody big brace in the way on a convertible that makes the plug much more inaccessible. A bit of 12mm square stock about 25mm long, a strong combination wrench to break it free and a ratcheting box end wrench to back it out and put it back ( or I assume some exotic Jag special tool ) are needed for the convertible

 

Yes I have the XK8 Coupe and feel fortunate the diff plug is more accessible then the convertible model. Thanks for the "Red Alert" regarding the convertible diff plug issue...

ER.

 

A great write up but I would question your topping up method (to fill until the oil dribbles out). The diff when dry, takes 1.8 litres or 1.9 US quarts and I can assure you that when this amount is added to an empty diff, the oil level does NOT get high enough to dribble out.

I may be wrong but you could be overfilling using your method. The way I did it was to firstly remove the old oil using a cheap hand vacuum pump then I put in 1.8 litres of fresh oil.

 

The diff fluid I pumped out (all of it, 1.9 qts) was black like mud (85500 miles) pumped in new Valvoline 75W140, vehicle transmission shifts like new, what a tremendous improvement it made in performance. My research indicated 75W140 was the gear oil to go with not 75W90. 75W140 gear oil also lowered the engine operating temperature, the engine temp gauge dropped when now driving all the time. What's up with that?

ER.

 

What quantity of oil did you add?

 

After evacuating all the old gear oil (it was black thick mud) I pumped in Valvoline 75W140 Synthetic gear oil (SynPower) that already has the additives in it. This gear oil can be used with both conventional and LS Diff's. Once I reached pumping in 1.9 Qts. of the above gear oil it began to back drain from the Diff fill hole. Noticeable/definite improvement in both engine/tranny performance while the engine running temperature dropped slightly. Order the the above gear oil online from Advance Auto for only $12.99 per Qt., and do an "in store pick up" otherwise you will not get your online order discount$$$ and be forced to pay $19.99 per quart. Valvoline SynPower gear oil is M2C-192A compliant, which it must be or XK8 Diff failure may occur. Diff change for XK8's at every 30,000-50,000 miles depending on how hard you drive the vehicle, no more then 50K for sure to be safe... Replacement XK8 Diff cost will burn you "Big Time". Imagine detonating your XK8 Diff all because you didn't spend $26.00, jack up the rear end and change the gear oil yourself at 50K miles?

E

 

See the below link:

https://sharena21.springcm.com/Publi...-ac162d889bd1:

 

See below link:

https://sharena21.springcm.com/Publi...2-ac162d889bd1

E.