The Tiger's engine was water-cooled, and heat was extracted from the water using two large radiators with two fans each. The fans, in the extreme rear of the hull, were driven by the engine via a dedicated gearbox.
Two kinds of engine were used in Tigers, the HL210 and, from May 1943, the HL230. The gearbox arrangements were different for each. Here I describe the fan drive for the HL210.
The gearbox
This is the fan drive gearbox for the HL210. It was bolted to six mounting points on the rear wall. A drive shaft from the engine connects at [A] and two shafts at [B] go to the fans. [2, see Tafel 44]
These photos show the gearbox removed from Tiger "131" at the Tank Museum. It is lying on the floor and is very dusty, but you can see its original red primer paint on the undersides.
[1] Survey of Tiger 250122, at Bovington museum, by David Byrden
[2] Kraftfahrgerät teil 3, Fahrgestell und Turm Panzerkampfwagen "Tiger", heft 60