In a Tiger 1, the rear end of the gearbox was supported by a mounting ring. This photo shows the mount and gearbox in vehicle #250122 at Bovington Tank Museum.
The mount was made of two cast-iron segments. The top segment could be unbolted to remove the gearbox. This is a photo of the rear of a mount, in its original blue-grey colour. Notice that the top segment has its part number embosssed on it; "021 D 2702 - 7". The first three digits, "021", identify the tank as a Tiger 1.
This side view shows the complex shape of the lower segment. It has three feet. These feet stood on rubber blocks 30mm thick and 70mm square, as you can see in the first photo.
The mount was installed in the floor of the tank, on the center line.
It was bolted to a an L-beam and a small tab. These were welded to the stiffeners on the floor of the hull.
The L-beam was between the first and second transverse stiffener.
In this photo you can see the L-beam, at the right.
This photo is from the Sturmtiger at Munster. The colours may not be original. You can see the mount, the gearbox and the front end of the drive shaft. The gearbox' ventilation hood is missing.
The small connector at the right of the photo is for the turret drive shaft. That shaft was removed during the conversion to Sturmtiger