why such a high failure rate for the XK, XJ differentials? Is there a fix?

 

No idea.

My S2 V12 has 640000kms, same diff, even the BW12 trans is untouched.
The S2 Daimler had 340000kms, same diff, new output seals, thats all.
The XJS had a Dana, no issues at 245000kms.
The S3 XJ6 "snotter", no issues either.
The XJ40 3.6, daughters car, survived her teenage driving prowess, and still going strong at 420000kms.

Clean oil, changed annually, is MY service care of ALL my Jags, maybe thats the key, dunno.

 

Is this really an issue? I have 230k on my car and only the bearings and oil ever got changed on the diff, plus a whole wack of poly bushings to make it rigid.

 

I'm not aware of an unusual failure rate of the old inboard brake differentials. I'd say they're as robust and durable as any other.

That said, a lot of them are running around low on oil. Checking the level and topping off is a bit of a hassle so it doesn't get done.

Seems to me, after 20 years on various Jag forums, the later outboard brake diffs are more likely to fail. The diff on my 95 XJR failed at just 77k miles!

Cheers
DD

 

There isn't a high failure rate. MANY have pushed these diff's well past 500HP in Jaguars and project cars that use Jag rear end components like Cobra racers. As long as you keep the oil in them you're good for just about anything other than fast high HP tracks in the heat.

 

I've had a number of XJ and XJS jags running since late '70's, basically the same diff in all these and never had one fail.
As mentioned the output shaft bearing need some work sometimes but other than that they are fine.
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Never seen a Jag diff fail. Only diff issue that comes to mind was my dad's '84 xj-s he had when I was a kid had a diff that whined. He really couldn't be bothered though so that car whined its way past 200,000 miles before the car succumbed to something else entirely! We used to joke that the old cat was howling in protest..

 

I think he is refering to the different diffs fitted to the XJ40, XJ81, X300, X308 and X100 models. They tend to fail on the bearing side of em. Meaning the input and output shaft bearings fail and whine... They are just cheaper made.

 

 

I think you are correct, and the op posted in the wrong forum as most of his other posts are in the XK and X300 forums.

 

im not aware of a problem with the rear diffs, iv been pushing some pretty good horsepower threw mine without issue for a while now.