From 1941, various proposals had been made for a self-propelled version of the 10.5cm leFH18. Krupp designed a special vehicle based on the Pz Kpfw IV components, using a smaller engine, hull and three-station bogies per side, with larger road wheels. Krupp's Pz Sf IVb had a partly-traversing turret which was open-topped. A Test Series of eight units was ordered. Production vehicles were to have the Maybach HL90 which gave 320PS. Production was cancelled because, on the subject of self-propelled artillery, official thinking was tending towards carriages capable of all-round traverse, with ability to dismount the weapon.
The Sd.Kfz. 165/1 was similar in design to the Heuschrecke, but did not have the chassis-mounted launching mechanism to remove the turret. After a series of tests, the Sd.Kfz. 165/1 was accepted by the Wehrmacht in early January 1940. In 1941, Krupp built prototype vehicles armed with the 105 mm leichte Feldhaubitze 18/1 L/28 (light field howitzer 18/1 L/28, abbreviated leFH 18/1 L/28) cannon based on a modified Panzer IV chassis. The prototypes were fitted with a smaller six-cylinder Maybach HL66P engine, which had a power capacity of 188 hp (140 kW). Although 200 vehicles were ordered, Krupp completed only 10 prototypes in the final four months of 1942.
Alkett now proposed an interim solution of mounting the 10.5cm leFH18 on the Pz Kpfw II chassis, and this was accepted as the Wespe (wasp). In a final attempt to have their special GW IVb chassis utilized, Krupp offered the design as the basis for the Jagdpanzer IV, designated Panzerjager IVb (E39) mit 7.5cm PaK39 L/48, but the normal Pz Kpfw IV chassis was again utilized.