Post-Newtonian <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi></mml:math> -like parameters and the gravitational slip in scalar-tensor and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>f</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>R</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math> theories

We review the fundamentals and highlight differences between some commonly used definitions for PPN gamma parameter ($\gamma$) gravitational slip ($\eta$). Here we stress usefulness of a gamma-like by Berry Gair ($\gamma_{\scriptscriptstyle \Sigma}$) that parametrizes bending light Shapiro time delay in situations which standard $\gamma$ cannot be promptly used. First apply our considerations to two well known cases, but conflicting results can found: massive Brans-Dicke gravity $f(R)$ (both metric Palatini versions). Although is always defined, it has general no direct relation either deflection or delay, hence care should taken on imposing bounds slip. that, any system with posed Newtonian limit, theories have $\gamma = 1$; while only values: 1 1/2. The extension towards Horndeski shows qualitative surprises, $\gamma_{\scriptscriptstyle \Sigma}$ constant this context (only assuming potentials approximated analytical functions). This implies precise study different impact parameters principle rule out complete action as an gravity. Also, comment consequences inferences at external galaxies.