
but to what?
a bit of over excited driving tonight has left the diff sounding a little worse for wear. it's never been great and even played up at sva!
what are my options?
everytime someone mentions a cossie lsd someone mentions driveshaft issues? is it not just a simple case of getting the shafts with the diff and
changing the whole lot? (i've got a drum brake rear)
if a lsd is going to be problems to fit then what ratio would i be best with? i don't race the car it just gets a blast on the country roads from
time to time.
finally is anyone selling a sierra diff?!
well, if you want an LSD, your best bet is one from a 4x4. I read the other day about cossy trackwidth differences causing the cv joints to bind. Plus
it might be a 7.5" diff. 
You dont want a cossie (2WD) LSD - just a 7" one is ideal. Found on any 4x4 (including cossie 4x4 and granada 4x4). Will all be 3.62 except for
a 2 litre DOHC xr4x4 which will be 3.92 if you want more spirited acceleration. What ratio you running now?
Unfortunately since you're starting from drums and push-in shafts it's not quite so simple. You've either got to go totally over to
the disc rear end, which will involve changing/modding your uprights/hub carriers, or creating hybrid disc/drum shafts with the bolt-on lobro cv
inboard and your existing tripode cvs outboard.
There is a thread around from somebody who did this. Took a bit of hunting to get lobro and tripode shafts the same thickness so the cv swap was
possible, I believe.
Liam
not sure about the diff, but I might know someone selling a whole seirra. will ask around if you want
Chris
I have a complete 2.0l back end if your interested, still attached to sub-frame.
Came off a 'C' reg sierra. Not sure what ratio, push-in shafts and drums.
Make me an offer if your interested. 
John I may be able to help check your U2U
Stick to a 3.92:1 ratio for fast road use which gives a good balance between acceleration and comfort/economy.
To go to 4.1:1, 4.4:1 or even 4.7:1 you'll be shelling out £700 for a new crown wheel and pinion! I have the 4.4:1 ratio which is great on track
but I do tend to cruise above 4K RPM (probably not much differnt from a BEC).
So far I've stuck with the drum rear end (converted to discs) for the weight advantage. Also my 1600cc 4AGE doesn't have the grunt to worry
my R888 tyres most of the time.