again this stuff is well documented. you don’t need to match the gear ratios a guy sells the converter on here

the xj40/300 trac lock is a piece of **** you need a new carrier. either an old powerlock with new plates, speedmaster, auburn, ATB or whatever you can find.

 

xalty nails it again.

 

The HU15 diff has a COLOR CODED sticker for the ratios
A BLACK X across the color coded sticker indicates LSD. (powerlok)

 

Thank you guys for the reply. The main reason I’d want to stay with the stock gear ratio is for mpg on the highway, but have traction from a stand still and if I get on it hard on a turn, have control. The OE traction control just isn’t going to work out for me.

 

I agree completely.

 

Yes indeed....if you have a need, then certainly you should address it.
The Duchess, in stock running gear works for me.

 

The 15HU can be made to fit into an X308. With the 15HU you can fit one with the correct 3.07 ratio made by a company that makes them very strong with propretary heat treating, What I then did was design and fabricate 30 spline axle shafts (to HRC58) and then fit torsen T2R LSD to those shafts. After years of abuse - the rear end is absolutely fine!

 

A lot of good info from among others Count Iblis. However, first and last: Get the very best snow tyres you can get. Second, put a couple of sandbags, 25kg each, in the trunk/boot. Third, drive carefully and leave the car at home on days with heavy wet snowfall. In addition to the above you can fit a quaife diff, but unless you can do the job yourself you are looking at minimum 2000 USD all in. You need to reshim using engineer's blue to ensure tooth contact is correct.

The HU15 plus noseplate from an XJ40 is plug and play mechanically, but at least for the XJR with 3.06 final drive you have the problem that the car will go into limp mode because no XJ40 had that ratio. The guy that made the arduino based CAN bus adapter to fool the TCM into thinking the ration is correct did not have any stock left last time I checked. The info is available though if you are comfy with arduino + some extra hardware. I have that project on the back burner until a few other projects are completed.

All that said, I ran my XF for years on the traction control alone here in Norway but the improvement with quaife that I have run the last five years is substantial.