This study examines the susceptibility of two filler materials (T46 6 M M21 1 H5 and G46 4 M21 4Si1, Ø 1.2 mm each) to solidification cracking, using an externally loaded hot cracking test. Although these filler materials are usually not critical in terms of hot cracking in engineering applications, cracking occurs when external loading is applied during welding. This was observed during welding under service conditions, e.g., repair welding of highway bridges under traffic loads. In order to characterize this behavior further, experiments were conducted on highly restrained fillet welds in an overlap configuration with 8 mm thick base material (S355J2 + N, 1.0570). The modified approach of the Transverse Motion Weldability (TMW) test is based on the transverse displacement of the lower plate relative to the welding direction at a controlled speed, corresponding to the induced deformation rate \(v\) in the mushy zone, initially set to 0.5 mm/s to initiate a crack and then linearly reduced to 0 mm/s. Gas metal arc welding was employed in this study, investigating energy per unit lengths of 0.8, 1.2, and 1.6 kJ/mm. The objective was to find and validate a critical deformation rate ( \({v}_{cr}\) ), below which solidification cracking stops occurring. Therefore, a new force-based evaluation method is presented. While both filler materials exhibited low susceptibility to solidification cracking under standard welding conditions, an increase in cracking tendency was observed with higher energy per unit lengths. The externally loaded test provides a quantitative assessment of hot cracking susceptibility. The results enhance the understanding of solidification cracking mechanisms and provide valuable insights for welding applications under high restraint, including repair welding of loaded structures such as bridges.