In 1944, Zahnradfabrik Augsburg equipped a normal Panzer IV H with a newly
developed hydraulic steering system. The so called "Thoma" (non-liquid)
oil drive transmission was installed and drive sprocket was replaced with
the new one. The power train consisted of twin oil pumps driven by Maybach
HL 120 TRM engine. In order to accommodate all the changes, entire engine
deck and rear was modified. In mid 1944, this prototype was fitted with
modified hydraulically operated turret.
Tests were carried on but were never concluded. At the end of the war,
this vehicle was captured by the US Army and was sent to United States
for further examination. This vehicle is still at Aberdeen U.S Army Proving
Grounds in Maryland.