Given the growing resistance of allied tanks to German anti-tank guns, plans were developed to categorically up-gun the entire range of German tanks toward the end of World War II. One possible answer was affixing the Schmalturm of the Panther Ausf. F to the Panzerkampfwagen IV Ausf. J chassis. The drawing above gives a good indication of what the conversion would look like.
Unfortunately, like so many other late-war German projects, this conversion was impractical. The chassis of the Panzerkampfwagen IV was severely overloaded by the schmalturm. Furthermore, it is doubtful the turret ring of the Panzer IV would have been able to accommodate the turret unless the overhang was widened (which was suggested in one schematic). However this would have further overloaded an already burdened chassis.
Every major German tank of World War II shared essentially the same design architecture. The engine was in the rear, but the drive sprockets were at the front. Therefore power was transmitted via a drive shaft through the fighting compartment (frequently under a turret basket). The major drawback of this system is that it raised the silhouette of the tank to allow for the drive shaft.
Prototype development of a special version of the Pz Kpfw IV with hydrostatic drive, which was ordered by the SS in July 1944. Placing of this drive at the rear of the tank, gave additional space within the fighting compartment, and a drawing dated October 1944, indicated that sloping frontal armour was to be a feature of the project. A prototype was built from a Pz Kpfw IV Ausf G.
Zahnradfabrig Augsburg built this particular Panzer IV. The design had no gearbox, and was not a liquid drive. Rather the "Thoma" drive allowed the primary Maybach HL 120 TRM engine to power two high-performance oil pumps which in turn powered two oil engines.
The results of the German tests on the vehicle were lost during the war. After the war, the vehicle was taken to the Aberdeen Proving Grounds to be tested by the U.S. Army (as they were working on their own hydrostatic drive project). The vehicle remains at the Aberdeen Proving ground today.