Carver Mead’s G4v gravitational framework identifies the gravitational scalar potential with the local speed of light c, and derives inertia from Machian interactions with all matter in the universe via both past and future light cones. We show that the Woodward transient mass effect — a predicted fluctuation in rest mass when internal energy changes in an accelerating system—emerges naturally from G4v’s time-symmetric Mach prescription. The mathematical structure of the effect (proportional to ¨ ρE, the second time derivative of energy density) is forced by the symmetry of the (retarded + advanced)/2 Green function, which identically cancels odd derivatives. The magnitude of the effect, characterized by an order-unity coefficient λ= ϕ0/c0^2 ≈0.72, follows directly from the Machian boundary condition that inertia is entirely due to gravitational coupling with the cosmos. This derivation closes a gap in the literature: readers of G4v who interpret the Abraham equation as a local field-sourcing problem obtain a Planck-suppressed effect, missing the Woodward structure entirely. We clarify that the Machian route—native to G4v as Mead formulated it—yields the transient mass law with no assumptions beyond Mead’s stated prescription and the standard strong-Mach absorber closure.

This is an early draft and not yet at preprint status.