Hi experts,
does anyone know if it is possible to swap the crown wheel and pinion in the X300 diff?
I'm thinking about putting the 3.58 diff (4.0 N/A diff) in my XJR (swapping out the 3.27) to see what difference it makes to acceleration...
Can I swap the crown wheel and pinion but leave the rest the same so I retain the LSD ?
it would raise revs about 9-10%, but I have 5 gears, and if one exceeds 140km/h and is caught by the constabulary, it is loss of license. So absolute top speed is not a concern.
thanks..

 

Why not just find a limited slip diff from a VDP or other car that already has the 3.58:1 gear setup?

I have 6 diffs from XJ40 and X300 sedans and some have the stripes with the BLACK X through them to signify the limited diff clutches.
The striped bar colors are the gear ratio and the black X is LIMITED SLIP.

The XJ40 or X300 are basically the same except for the thread pitch bolt/studs on the pinion end and the output flange fasteners (bolts hex vs Torx).
They are interchangeable in the rear suspension cage.

It is easier to replace the entire 'pumpkin' than to mess with gears and lash setup.

 

Yes, you can do that. You will have to make sure that all your clearances and backlash is correct, and that can be time consuming. It's vital to get it right, so patience and thoroughness is the name of the game.

 

Thanks for the quick replies, guys.
ive just been out in my car - screenshot from OBDII.
revs at 100km/h GPS speed would rise to 2150 in 5th gear with a 3.58 diff. I could live with that

 

pretty sure the idea behind the 3.27 was to get to 60mph in second gear with the manual, autos really got the short end of the stick with the tall gears

 

I changed my VDP from a 3.58 to 3.77, simply because I was able to find a 3.77 with limited slip, and I didn't know at the time I could have changed the internal components from an XJ40. I found at 110 km/h cruise that it cost me about 2 mpg in fuel economy.

 

I can do 0-60 mph in 5 secs, using 1st then 2nd gear.
my car is manual, with the Powerhouse supercharger drive pulley, and Andy’s reprogrammed EPROMs, otherwise standard.
I think I saw some figures on the net the other day, that a std auto XJR does 6.6 secs

 

When I had an XJR I went from 3.27 to 3.58 and was happy. The response and acceleration was better. Not a huge difference, but it was noticeable. I lost 1-2 mpg at highway speeds.

I wasn't planning on the change. It's just that my diff failed and I found a rebuilt 3.58 LSD for just $400 shipped on Ebay. It was a Coventry West unit, still in the crate, that somehow ended up in the hands of a liquidator. Lucky me !

Cheers
DD

 

I found the initial acceleration on my XJR a bit sluggish. I bought a 3.58 open diff & swapped the LSD over to that, but I was lucky to have a mate with the right tools / spacers / shims. It's not a straightforward job. If you can find a whole diff to drop in that is easier, although the whole rear subframe & suspension is built around the diff. However, the gearing is much more to my liking & I don't mind the extra revs at cruising motorway speeds.

 

there are some informatic videos in you tube on the dana 44 type (which the jaguar 15hu is close cousin) like below

 

you can get ring and pinion with just about any drive ratio like 3.73 4.56 etc on ebay that fit the x300
https://www.ebay.com/sch/i.html?_fro...+4.0L&_sacat=0
also on ebay you can get a posi traction that firs in the dana 44 which is the differntial that the x300 uses
https://www.ebay.com/sch/i.html?_fro...+XJ6+Base+4.0L

 

You need a 19 spline posi or else you’ll have to make custom output shafts, Auburn makes one for 3.73 ratio and down.

 

those Auburn one are cone type locks, right?

 

Yes, and they’re fully disposable units. Upside is they’re pretty cheap.