We investigated the magnetic properties of Gd2Fe17-xMx compounds with M = Al or Mn. We performed low-field magnetization measurements to obtain values for the Curie temperature and high-field magnetization measurements (B less-than-or-equal-to 38 T) on powdered samples that were free to orient themselves in the field applied to obtain values for the saturation magnetization. From the high-field slope of the magnetization we derived values for the R-T coupling constants n(RT) using the mean-field approximation. We find that substitution of Al or Mn, although it reduces the Fe magnetization in different ways, has only little influence on the intersublattice coupling strength.