This kind of small
anomaly cannot be detected in the Voyager probes (and other missions) using the same methods:
"The Pioneers were uniquely suited to discover the effect because they have been flying for long periods of time without additional course corrections.
Most deep-space probes launched after the Pioneers either stopped at one of the planets, or used thrusting throughout their mission.
flew a mission profile similar to the Pioneers,
but were not spin stabilized.
Instead, they required frequent firings of their thrusters for attitude control to stay aligned with Earth. Spacecraft like the Voyagers acquire small and unpredictable changes in speed as a side effect of the frequent attitude control firings. This 'noise' makes it impractical to measure small accelerations such as the Pioneer effect; accelerations as large as 10−9 m/s2 would be undetectable.
Newer spacecraft have used spin stabilization for some or all of their mission, including both Galileo
These spacecraft indicate a similar effect, although for various reasons (such as their relative proximity to the Sun) firm conclusions cannot be drawn from these sources."Source: http://en.wikipedia.org/wiki/Pioneer_anomaly#Indications_from_other_missions