Today I pulled the Diff out of the car. This thing is way over-engineered. You pretty much have to take the whole rear suspension apart to get it out of the assembly.






My goal is to rebuild it myself. I'm hoping that with the collective knowledge from all of you guys we can put together a thread which can be a reference to anyone trying to do the same thing as from what I see the differential failures are pretty common. I'll be updating this and posting pics as I go.


Feel free to chime in with any info you might poses on this subject.

 

So the axle is Salisbury 14HU right?

 

Should be a GKN 14 something or other.

Once you peel it apart, see if there is a squat sealed cylinder that forms part of the gear carrier in there.

 

XJR diffs - PistonHeads mobile


Interesting read there. I'm wondering if it's possible to fit an LSD differential with steeper gear ratios from x300 xjr to the x308 chassis?

 

Yes. You also need the front mounting plate because the diff input is offset. Be aware that the TCM *may* need to be reprogrammed.

It may be of the salisbury type, but the manufacturer is GKN.

Now, what about that cylinder in the gear carrier?

 

I didn't peel it apart yet. I started but wanted to do more research.

I did find out that one of my brake pads in the rear disintegrated as soon as I took the caliper off when taking this out. Also, the brake shoes for the e-brake were loose too!

I drained the fluid and it didn't look too old and didn't smell bad. It looked slimy green and seemed a bit metallic.

 

As far as the front plate. Can that be modified? Drilled, welded etc?

 

It has been done that way, but since the yard that is going to have the diff probably has no use for the mounting piece, just buy it with the piece. It's a bolton between the X300 and X308.

 

x308 units seem to be much easier/cheaper to find

 

Hi Adam, looks like the start of an interesting thread......hopefully some of the other guys with much more knowledge than I will chime in soon.

I for one will be checking back to see your progress

 

Welcome to the world of Jaguar rear suspension!

unrelated, but a recent E Type rear rebuild - 50 years old, it's akin to engineering archaeology.



A powerloc LSD is in my future. Quaife option is there but from what Avos has mentioned, it doesn't give the slide/lock feel of the Salisbury type LSD. I'd rather use an XJ40/X300 LSD and rebuild it. Ratio's?! 2.88/3.07/3.31/3.57/3.77/4.09 ++. TCM reflash?!

 

Not sure if the x308 diffs are GKN, the crown has the word DANA marked on it.

Have also searched for long to find the right preload settings of the pinion, but no one have offered them, and obviously I haven't found any documentation. Most re-builders seem to work based on experience, and it is imperative that you have that as when not set right it will cause bearing issues and in the end destroy your diff. This makes this diff somewhat more difficult than the older versions with a crush ring to get to the right preload setting (not sure though, as this is not my area). It can also be very time consuming to get it right, as you need to disassemble the diff every time if you need to make a modification, and here is a risk that a re-builder would take a shortcut…

As it is a lot of work to swap out a diff (especially at home with just stands), I opted not to go ahead myself to risk it, and left it to a specialist (which I luckily have found). Nevertheless I would like to try it once, so hope you’ll find out more.

Going to a different rear end ratio is costly as it requires a reprogram of the TCM, I think it was $1500 or $2000 or so.

 

Why does the TCM need reprogramming?

 

The TCM uses the wheel speed sensor (ABS one) to verify the actual selected gear, so changing the diff ratio will change the expected output speed, and you go in limp mode.

 

Have you experienced that? I see a lot of mixed info on this. How hard is it to reprogram the ECU with the correct ratio info?


EDIT: My buddy owns a Ford VCM is that something I can use to recode the correct Ratios in the TCM?

 

No, haven’t experienced it myself and it is also long ago that I investigated it. The mb gearbox doesn’t have an output speed sensor, so the only way to know for the gearbox if it is in the right gear is via the wheel speed sensor, and if not within a certain margin, it will throw a P0730.

Have searched very long for companies that can re-program the MB TCM, there are very (very) few, and prices are also extremely high, seems that to create the new maps it takes a lot of time, that’s all I know.

What mixed info do you have then?

 

Google searches seem to point me all over the place. Can anyone confirm if it can be done with Ford VCM? My buddy claims that it's the factory scanner.

 

JUST CAUSE ITS A FORD VCM DOESNT MEEN IT WILL/WILLNOT WORK. iTS THE SOFTWARE THAT DETERMINS COMPATIBILTY.
PINION PRELOAD 25-35NM WORK WELL ON MOST ALL DIFFS. IF YOU TAKE OUT THE OLD/NEW BEARINGS AND RACES YOU CAN MACHINE THEM DOWN TO BECOME "SETUP" BEARINGS FOR PRELOAD. BUT I CAN ALSO TELL YOU THAT IN ALMOST EVERY CASE YOU CAN SETUP WITH THE PREVIOUS FACTORY SHOMS AND YOULL BE RIGHT ON. IMO THAT ITS THE CASE THAT DETERMINES MORE THE SETUP THAN THE NEW GEARS. ALSO TO IDENTIFY A POWER LOCK DIFF YOU LOOK FOR THE COLORED BAR TAG WITH BLACK X'S ON IT. THATS A POWERLOCKER. THE COLORED BARS REFER TO THE GEAR RATIO INSIDE.
nOW IDE LIKE MORE INFO ON FOR SURE ABOUT TCM REFLASH BECAUSE I DONT REMEMBER THIS APP. IDE LIKE TO PUT A SET OF 4.09'S IN MINE AND SWAP IN THE NEW POWER LOCKER I HAVE OUT OF THIS OTHER DIFF SITTING ON THE FLOOR SINCE NO ONE SEEMS TO WANT TO BUY IT

 

The jaguar tool can't reprogram the mb tcm unfortunately.

 

Well I talked to my buddy. He says that he has the Jaguar software in the VCM. He's supposed to stop by tommorow to see if it will pick up the TCM and if it will let us change things.