Ford Freestar and Ford Taurus Transmission Failure
The Ford Freestar and Windstar share the same automatic transmission as the Taurus and its cousins, the Sable and Continental, which suffer the same problems with failure. The worn shafts in this photo are from these transmissions, and the damage is caused by a poorly designed pump shaft bearing, which the shaft rides inside. We install an upgraded bearing that alleviates this problem. Another issue is worn boost valves for main line pressure and torque converter clutch application. Earlier problems with these vehicles were a cracked aluminum forward clutch piston, but that was corrected back in 1995 using an upgraded steel piston. Any information you see related to a cracked aluminum piston on newer Ford Windstar, Freestar and Taurus automatic transmissions is inaccurate.
Ford Cracked or Broken Transmission Cases
On many of these units, the final drive differential has a weak ring gear. Hard use can cause the differential carrier gears to create enough load to break the ring gear, which cracks the transmission case. This usually causes a lot of transmission fluid to leak out. Running the vehicle low on transmission fluid can cause catastrophic damage to the transmission. Heavier cars or minivans such as the Windstar and Freestar appear to suffer from a broken transmission case more often than lighter vehicles like the Ford Taurus as a result of the added weight on the transmission.
Transmission Slipping Gear Shifts Caused by Worn Pressure Boost Valves
While transmission slipping is often blamed on the pressure control solenoid, the culprit is usually a worn main line pressure boost valve. This valve controls pressure within the main transmisson hydraulic circuits, so all gear shifts can be adversely affected. The valve piston is cylindrically shaped and is designed to fit snugly within an aluminum sleeve. Because the pressure valve is fairly short relative to its height, its leading and trailing edges tend to wear out the sleeve. The height to length ratio, known as aspect ratio, has a directly proportional impact on the rate of wear between the valve plunger and the sleeve. Assuming the height remains constant, the shorter the valve, the faster it wears out.