Ford Mondeo 2.0l Estate 1998 Automatic Gearbox Problem?

When I turn L or R (OK when straight) get a clicking sound that seems to be coming from the automatic gearbox. Particularly bad when turning at low speed. Usually OK when turning at higher speeds - odd click. If turn in a tight circle then get constant clicking - both ways. Is it the gearbox? Suspension is OK - right CV boot split - some grease lost. Many thanks.