i've just swaped out the knackered gearbox on my 1996 c230 4 cylinder petrol 722.6 5speed. well the replacement is out of a 1999 e220 cdi. fitted fine, just had to swap over the output flange. but there was a cable going into the rear of the box next to the propshaft that was not on the e220 box. now box is in and driving well, but i don't know what the cable is that i haven't refitted? not the cruise control cus that still works so what is it?