Hello! Searched but did not find exactly what I was looking for and thought that it might be a good idea to have a thread stating what will fit and not. As there are quite a few out there with problems/ruined diffs this seems to be good thing...
So mainly, my basic q is:
Is XJ8 3.2, 4.0 and 4.0 supercharged diffs fully interchangable (except for Mexican differnet ratio)?
Have found a XJ8 3.2 diff that I want for my XJR-98...
Thanks in advance!
/Per in Sweden

 

Per, the 3.2 is 3.27:1 ratio, the 4.0na and 4.0sc are 3.06:1 if you fit the 3.27 your car might not work as the trans module isn't programmed for that ratio.

 

Aha, ok, I was told by Avos that all used the same but the ones for the Mexican market. OK, so that should as far as I understand mean that I can use one from a 4.0 non SC model! thats good news as I got contact with a person that have several units for sale, but quoted 400£ for just a XJR8 diff, compared to 120£ for a normal one....

Anybody else with input?
PS.
I just want the car to stop making that odd huming noise between 50-70mph, don't want to change ratio or get a LSD for better 60 fot times he he. I think that they are allright as is he he....

 

Sorry, keep forgetting about the 3.2 cars ;-)

 

Well, they are quite far from what you have created he he...
No problem, was not trying to be rude. Just wan't to make sure that I buy something that will fit and not require rebuild of mech or electronics.

Thank you all for the input!

Cheers!
/Pelle

 

No Problem, didn’t take it that way. It is a good thing actually, as that means you can get a 3.27 gear much easier for those who want more torque to the wheels. With a little bit of luck I hope to confirm in a week that the TCM for the 4.0 XJR/XKR can be adjusted for this gear ratio for about 300 euros.

 

Although I have no issues with the diff on my 1998 XJR, I have heard of a couple of instances of the diffs giving up the ghost. If I am unlucky enough to be looking at that any time soon, are the XJR diffs, and the 4.0 N/A diffs a direct swap?

 

Hello, I have also a straight question on this topic : is the X300 (XJR) differential a LSD? Second one, if it is, is it possible to be fitted inside the X308 differential shell, keeping the own X308's wheel and crown to avoid ratio changing and electronic errors? I know about Quaife LSD option diff, but it's a little pricey.

 

LSD was optional on the X300, so some have it, but not all. Don't know if it fits inside the X308 diff though.

 

Thank you all for contributing to the thread!
Dstary, exactly what I am trying to find out!
JKo, same here I am affraid, don't know if it will fit.
Cheers!

 

As far as I know the 4.0 are all interchangeble from the 4.0 cars (being SC or not), even from the 4.2 XK8/R models.

 

I'd thought I'd cleared this up. Stated the ratio too.

 

Thanks Sean. I saw you state that the ratios were the same for the 4.0L cars (supercharged and N/A), but I didn't know whether they were the same diff. By the looks of it they are, and you could happily swap diffs between supercharged and N/A cars.

 

Some more info,
As I wanted to know how you can tell the ratio for a specific diff, which is not in vehicle, I searched to see if there where any markings or id no on unit. As it turns out, there is. There is a small sign about 15mm wide and 60mm long, mounted on between two bolts holding the aluminium aft cover. On this there is a first some id no and than ratio!!! Regretably, this sign is of ordinary steel and as it seems unpainted, which than gives that it will be rather rusty in northen europe climate, but still probably posible to see what is punched in if some light griding with paper is done. Thought I let you all know! Cheers!