hi ! could anybody tell me the ratio of my diff . its from a cortina and has the following numbers / codes on the case in various places . N3 7J22 105E 4025E .

Probably best to just measure it. Is if fitted to the car at the moment?

If it is then see how many turns of the prop are needed for one full rev of the rear wheels (might need to average it if the rear wheels move at different rates).

according to haynes, for the mk4 and 5 capri, there were only 3 diff ratios.
1600cc, standard was 3.89:1
1600cc option and estate car 4.11:1
2000cc all varants 3.75

hth

edit, just seen from your last post, its a mk2 cortina axle. as above, your best bet is to measure it manually as above

[Edited on 12/11/10 by blakep82]