hi I have just picked up a ford sierra 3.38 diff I have looked at most of the sierra diff numbers but can.t find my number anywhere no.s are 83 bg 4006 lc and 4 a 338 3 a 16 these are on the tag on one of the diff bolts any ideas please thanks

The only real way to find out what it is is remove the rear cover and the ratio will be stamped on crownwheel

hi ok thank you I was hopeing I wouldn't have to do that cheers bob

You can count the turns, if you lock one output shaft then the other side is multiplied 2:1 by the planet gears so one turn of the pinion is 6:76 turns of the free side.

[Edited on 3/12/15 by mark chandler]

Check out this page.
http://www.super7thheaven.co.uk/components/sierra_rear_differential/

83 bg 4006 lc and 4 a 338 3 a 16

Its a 3.38 if the tag is correct.

thank you one and all