I would go thru the effort to keep the 3.58, personally.

Your suspension swap idea sounds good to me !

Cheers
DD

 

The 3.27 was so there would only be 2 shifting points between 0 - 60 mph advertising times vs. 3 shifting points with the 3.58

it does make for better fuel mileage but I don't know about off the line performance difference

If you do change the pinion gear it would give you the chance to change the differential output bearings to stay ahead of this troublesome bearing

4.09 is a gear to flirt with if you can find one but a Dana 44 set is a option , the 44 may not be correct

https://parts.jaguarlandroverclassic.../brand/jaguar/

 

Oliver ,

The 4.09 I believe is used on the 3.2 liter version of the same 4.0 liter block to make up for it found on your trips to England

Whether it's metallurgical strength rated is another question

Dana option ?

 

Thanks for this, my car feels very strong and I don't have any great urge to get it moving faster with a lower gear ration. I may use the engine in a 76 xjc ultimately with a getrag box but for now I'm finding I'm enjoying driving the xj12 as is.
The 'troublesome diff output bearing' probably needs some attention sooner rather than later based on what I've been reading here though...
I found a rear tire had severe inside edge wear last week, was wondering if that had been caused by a rear suspension/drivetrain issue or whether the PO had hidden it back there as the car currently is is keen to turn left due to front end issues

 

Now you have me lusting for a 4.09 diff.

But, I doubt there's one around. As LP says, they were UK only I believe. Maybe Coventry West has one.

Years ago I found a S1 XJ 2.8 import, and pulled the 4.09 for my car. It made a big difference. It would actually spin the tires. I had a T700 trans, so it still rev'd okay on the highway.

It's been said often on these forums that a diff swap is the cheapest way to get more acceleration. I also have a S3 VDP with 3.31 and the difference is quite noticable. I know DD has done the same. I have a 3.58 from an XJS waiting for a project.

Best to all.....

Rob