This study discusses the effect of Post Weld Heat Treatment (PWHT) and welding efficiency on the axle housing of Steel Automotive Press Hot (SAPH) 440, where the axle housing is a critical component in automotive vehicles. The research was conducted using the Double-Electrode Gas Metal Arc Welding (DE-GMAW) method for welding efficiency, with butt joints. Macro- and micro-structure tests, as well as hardness tests using the Vickers Test, were also performed. These tests aim to provide insights into welding quality, defects, and the effect of PWHT on SAPH 440. From the results, the ideal welding parameters for Axle Housing welding are 300 A current, 29 V voltage, 140 cm/min welding speed, and 110 cm/min filler wire speed. Macrostructure testing shows that the obtained sizes exceed the standard, and using the DE-GMAW allows axle housing welding to be performed faster than conventional methods. Microstructure testing shows a difference between non-PWHT with ferrite grains of ± 5–10 μm and with-PWHT specimens with larger and coarser grains of approximately ± 25 μm, due to grain growth. Micro Vickers testing shows that the non-PWHT has a higher hardness value in the heat-affected zone (HAZ) area, around 176.28 HV, while the with-PWHT specimens have a lower hardness value in the HAZ area, around 150.64 HV. However, the with-PWHT is much tougher, proving that grain growth and reduced internal stress have occurred. The selection of SAPH 440, solid wire as filler, and the use of MAG gas are a suitable combination for axle housing welding.