classic rear diff question
 

managed to find a 3.9 diff advertised on another forum for £30 n I got matching rear drive shafts for another £20 just in case.

2 questions:-
firstly, if i turn the diff input shaft it should turn 3.9 tims for the output shafts to turn once? cuz its doin just over 4 turns.

n secondly, it has a sensor or something electrical stuck in the bottom back plate of the diff. my current one doesnt have this. anyone know what that little electrical gizmo in the back of the dif is ?

I'm thinking maybe the plug I's diff oil temp, not all models had this.....

some models have a "diff oil temp warning"..........often Forester's

easiest way to check, presuming its still out of the car is to whip the back cover off, count the teeth on both the larger crown wheel and smaller pinion gears and then divide the larger by smaller to get ratio.................