Oil & Fuel Gear Box Oil on a Mahindra 4500 4 x4

[Mahindraman4500]

Hello, just wanted to ask if anyone out there has changed the transmission/Gear box oil on a Mahindra4500-5500 or 6000 tractor - crawling under the tractor - Not sure which bolt is the drain plug - this model of tractor calls for the 80-90 gear oil.

Thanks for your help.