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Ford Explorer, Lincoln LS and Mercury Mountaineer Transmission Service and Repair

Today, these 5 speed transmissions are most widely used in the Ford Explorer as well as the Mercury Mountaineer. We also see some Lincolns and Jaguars that use this transmission type. The unit has many different variations known by the following designations: 5R55-E, 5R55-W, 5R55-N, and 5R55-S. Throughout many years this transmission has disappointed car, truck, and SUV owners with its poor reliability and expensive repair bills. These automatic transmissions are known to have mechanical, hydraulic, and electrical problems which vary among the different models.

Ford Explorer Automatic Transmission Problems

Ford started producing the A4LD in 1985. It was essentially an overdrive version of the C3 transmission, which was produced in the 1970’s for smaller vehicles such as the Pinto. In 1995, Ford began producing electronic versions of this transmission, which we see variations of today. These models are relatively smaller and lighter than the other rear wheel drive and 4WD car and SUV transmissions that Ford produces, limiting their torque handling capability. This issue has been a problem for owners and often causes premature transmission failure, especially in the heavier Ford Explorers and Mercury Mountaineers with 4WD and larger 4.0 and 4.6L liter engines as the transmissions were not ideally designed for these heavier units. Ford has made changes over the years including increasing the number of pinion gears in the planetary carriers. Later carriers were also strengthened by upgrading from aluminum to steel.

Ford has made numerous changes to this transmission over the past 20 years. In 1995, the transmission was redesigned and became electronically controlled, bringing new diagnostic issues. In 1997, another ratio was added between the existing 1st and 2nd gears, creating a 5 speed. There are 4 major variations of this transmission, each having multiple issues. These problems are addressed by using upgrades from companies such as Sonnax and TransGo.

Here are some fundamental problems that exist and the upgrades we use to correct them. Many transmission malfunctions are due to wear in the hydraulic mechanisms of the transmission; they include the valve body, the canister valve in the pump (not the pump itself), and the overdrive and intermediate servo pin bores in the case. For more information about bore wear, click here.

Wear of Valve in the Ford Explorer Transmission Pump

The pump flow control valve is located in the front transmission pump, and wears out at a fairly predictable rate. The valve in heavier Explorer trucks may fail a little sooner than it would in a Jaguar. Replacement valves are made by a number of companies, which use a harder grade of steel, significantly reducing the rate of wear. We use an upgraded pump flow control valve made by Sonnax, which should outlast the lifespan of the vehicle.