To fit a Sierra LSD diff into a 'Standard' Drum braked back axle.

(Thanks go to Colin King for doing it first, and finding out the problems!)

If you have the Disc braked Sierra axle, with the heavy duty drive shafts (Bolted to the diff and hub unit with Torque bolts) then You can just change the diff unit itself. but if you want to put an LSD diff into your previously 'Normal' back end this is what you do;...................

You would be best to remove the whole axle assembly, and then remove the piece parts later at home, so that you don't forget anything.

You will need, the diff itself (obviously) both driveshfts, (these are held on with Torque bolts, T45 size.) the wheel hubs (these need to be pulled off using a puller) the hub bearing assemblies, the rear callipers & brake set ups (It's good practice to fit new disc's & pads, and check the callipers are OK, reconditioned ones are approx. 43 each)


Undo the large nuts on the drive shafts whilst the axle is still in the car if you can, I believe they are 41mm socket sized, I have a 15/8" AF socket that does the trick.

If you find that they just won't undo, then a trick that I use, is to grind down carefully, until you get very close to the thread, this weakens the nut, and it will undo easier.

Remember that the nearside of the car has left-hand threaded nuts, you can see the 'notches' on the corners of the nut, this denotes Left-hand thread.

axle nut.jpg (13650 bytes)

The main problem with this conversion (apart from having to change over the brakes to disc's) is the clearance between the 'wishbone' casing, and the Lobo joint that connects to the hub unit, i.e. there is none!

So what you must do, is support the wishbone on the trolley-jack, then with a large hammer and a drift, dish in the wishbone casing where the Lobo joint will be, make sure that you do this enough or you're going to make more work for yourself (I know! I had to do it again!)

If you have contacts, you could also get approx. 4mm turned off the diameter of the flanges either side of the Lobo joint (these are slightly bigger in Dia than the joint itself)

OK, remove your old diff unit, and replace it with the LSD one.

Now clean up the large hole in the wishbone so that it takes the boss of the hub bearing casting (A quick run round with a dremil type tool is all that's needed) fit the hub bearing casting assemblies.

Then uncouple your shocker to allow the wishbone to drop down more, feed in the driveshaft from behind (note the N/S shaft is shorter than the O/S one) locating the other end at the diff, jack up the wishbone, and refit your shocker. Put a couple of bolts into each end of the driveshaft & tighten them up. Fit the wheel flange, this will need persuading with a nylon hammer, fit the large nut & washer to the driveshaft and by jamming the wheel flange with a bar, nip up the large nut.

Now turn the wheel flange a few times and check if the lobo joint flanges have rubbed on the wishbone casing, (mine did first time, so the shaft had to come out again for further treatment to the wishbone with the hammer & drift) Once you're happy that the joint isn't rubbing the case, you can fit all the bolts & tighten them up etc.

Now you have to sort out the brakes. Then tighten up the axle nuts............Bloody tight!!!

(See the other article, where I fitted disc brakes to this car previously)