Greets, I changed my differential (afaik no LSD) original blackish oil to Castrol Syntrax Long life 75w-90.
When diff is cold, it makes no extra sounds but when it gets warm from highway driving it starts to give pretty loud 'screeching' noise at very slow 90 degree crossing turn.
So looks like oil gets too thin when warm and causes noise as original oil did not exhibit this.

Any suggestion what inside diff can cause noise? and recommendations for new oil? 75w-140? I only drive car on summer.

Did you rerill with the same amount of oil you removed?

Gus
JagRepair.com - Jaguar Repair Information Resource

Pretty much, removed old 'gruel' w/vacuum and refilled until flowed over from rear plug. I think that new volume could be bit more than original due loss of oil by 20 year old car tho.

Are the symptoms like this thread of Supersprint's?
https://www.jaguarforums.com/forum/x...0/#post1811547

I had the dealer do mine with original spec gear oil. It was too hard to do it with the brace installed for stiffening the convertible. Took them about 3 hours to drain and refill. No issues

Yes! Exactly same uuuuuuh sound, only exception that does not occur when diff is cold for me.
So looks like bye bye Castrol and I'll do second change oil to 'Red Line 75W90 GL5+' next.

Be careful changing diff oil. The right stuff is Castrol Super 90 which is not multi weight, oils that have a winter weight below 90 are too light. Super 90 is very hard to find. If you have chattering, the spider gears are not lubricating right and you need to resolve it with a different oil. My suggestion is to leave the diff oil alone until the diff fails, as changing it may hasten that day.

Are you actually telling this guy to wait until his differential rips itself apart and then just replace the differential? Or am I reading that incorrectly...

I guess oldmots meant that 'do not change sealed-for-life-original oil'..

Anyway, changed oil to Red Line 75W90 GL5+ and no more scary 'uuuuuh' sound when driving slowww circle after 20 mil/65mph of highway drive

Weird, I 'investigated beforehand' that Castrol Syntrax was good stuff for XK diff but unfortunately missed supersprint's post