Ford Aerostar Transmission Replace/Remove

Trans Pressure Shifts Seem Week Part Throttle How Can I Confiim Wether Its A Seliniod Or A Hydraulic Issue,the Fluid Was Just Changed Issue...

Hi There, I Have A 1996 Ford Aerostar With The 4.0l V-6 Which Ran Perfectly Up Until Mile 268,797.1 The Van Was Towed Home But Still Moves...