Hello Members
I have a 07 XK convertible 73,000 mi. Is Castrol Transmax Limited Slip 75W-140 the only fluid that should be used when changing the fluid? If not what else can I use?
Thank You for your help
Bob Mitchell
Danbury, Ct

 

Any Ford spec M2C-192A synthetic will do.
You do not need to add a friction modifier or a viscosity control fluid.
There are a few brands that excel at low temperature and high temperature flow and lubrication.
RedLine, Lucas, RoyalPurple have good reputations.
I change mine every 50k kms, along with the transmission fluid and pan.

 

Don't use a limited slip oil unless you have a limited slip differential. Any non-LSD 75W-140 GL5 gear oil will be fine.

Richard

 

Any of those brand name gear oils would be fine. I used Valvoline. See this link for my experience in changing the diff oil.
https://www.jaguarforums.com/forum/x...4/#post2251156

 

Btw, I do like you chose 75W140 as opposed to a theme of using 75W90.
Correct, a “friction modifier” = “use for limited slip”. Unfortunately, the stock diff in this particular car has an open diff and it wouldn’t be needed.

 

Thanks much
Stay Well

 

On the 2008 XKR diff, not sure if the XK is the same. There is no drain plug for the diff oil. So you either have to remove the diff cover or suck the oil out from the fill hole. I'm running 75w-140 Amsoil severe gear oil. If you are going with the sucking the oil out method, make sure the fill bolt can be crack loose. Go for a spirited drive and then suck the oil out. Its easier for the thick gear oil to flow when its nice and hot.

 

Or tap a drain hole and source a magnetic plug…

 

Nah, it only takes a couple of minutes to suck out the old fluid and only done every 50k km if ever!

 

Guy. one last question. The car I have is I believe a base model XK. Other than heated steering wheel. So, all base models do not have a limited slip diff.
Thanks Mitch

 

My understanding is that the XK and XKR 4.2litre are all open diff. Not much options for aftermarket quality LSD apart from Quaife LSD for these models.

 

Yes, whether an xk or xkr, ‘07 -‘09?? were not provided with limited slip differentials.
You had to upgrade to an Aston Martin for that feature ;-). Or do what was suggested above, source a Quaife LSD,
and due to its mechanical nature, a improvement in my mind. (That should get this forum active, lol).

 

On the 2007 XK, please, what is the volume of differential oil? I have read . #1. 950ml , #2.. over a liter. #3 Drain and fill to fill hole.

 

Spec (workshop manual) defines 1.25 l.

Some try to be smart, lookup the FoMoCo reference and state that volume. The problem with that is they have not taken into account the custom rear cover.

Volumetric expansion occurs here due to heat. Don’t overfill!

 

#3 Drain (with a pump unless a drain plug has been added) and refill to fill hole.

Richard

 

FoMoCo offers the engineering for this on thier truck maintenance site but, this is a fair “readers digest” assessment:

https://newlygen.com/2023/09/21/can-...rential-fluid/

 

Our differentials have a vent, and it is unlike most, that don't have a one. Mind you, it has to be cleaned every once and a while.

 

From my experience, I would say that most differentials do have a vent rather than the other way around, although I'm not really sure what this has to do with the thread?

Richard

 

In a pinch (fill plug stuck) the diff can be filled using the vent.