Hi Riaz, welcome to the forum!
I'm not going to be able to assist too much, but if anyone can, and I'm sure they will offer to, they will want to know exactly where your leak is located.
Rear pinion suggests the rear differential where the pinion (attached to the rear propeller shaft) enters the diff casing. Am I correct?
Otherwise it could be rear pinion on the transfer box, or some other rear pinion... there's several.