The 1st generation (91-94) Explorer was released in 1990. Powered by a 4.0 liter, 155 hp V6, Ford Explorer transmissions were either the 4-speed A4LD automatic or the 5-speed M5OD manual. Four-wheel drive versions were equipped Borg Warner’s 13-54 part-time four-wheel drive transfer case. The shift on the fly design of this transfer case allowed shifting from two wheel drive to high 4 at moderate speeds. Explorers came with an 8.8-inch rear axle in a variety of axle ratios and could be ordered with a limited-slip option.
The A4LD was a common source of complaint as it could not cope with high loads and extended towing. Later versions with improved cooling helped alleviate the problem. The A4LD was a modified version of the original C3 transmission design. Basically, the addition of an overdrive gear and EEC control were the major design upgrades that made the C3 the A4LD.
M5OD transmissions are manufactured by Mazda and are manual 5-speeds with overdrive. There are two variants to this transmission, the R1 and R2, with the R2 being designed for medium-duty applications. Manual Ford Explorer transmissions use the R1 version.
Explorers of the second generation, produced from 1995 to 2001, received two engine options and four transmission choices. The Windsor 5-liter V8 and the heavy-duty 4R70W 4-speed automatic transmission were added to the lineup. In 1998, concerns over the 4R70W’s durability compelled Ford to replace the one-way roller clutch with a mechanical diode to promote longer service life and extra holding capacity. 1997 saw a 205 hp overhead cam V6 being made available, along with a 5-speed automatic. The A4LD was upgraded to electronic control, which resulted in the creation of a new transmission family. These became known as the 4R44E and 4R55E. These two are practically the same transmission design, except for the fact that the 55E is duty-rated at 550 ft/lbs. versus the 44E’s 440 ft/lbs. The 3rd generation Explorers (2002-2005) also used the 5-speed M5OD-R1HD manual transmission and variants of the 5R55 5-speed automatic. While mechanically alike in comparison to the 4R55-series transmissions (except for the additional forward gear), these new transmissions featured precision computer controls as well as adaptive shifting. While all variants of the 5R55 are fundamentally similar, specific needs and applications will be indicated by the transmission’s suffix, e.g. 5R55W or 5R55S.
Fourth generation (2006-2010) Ford Explorer transmissions are the holdover 5R55S 5-speed automatic and a newly-introduced 6R 5-speed automatic. Designed and produced at Ford’s transmission facility in Livonia, Michigan, it is intended to be used in longitudinal drivetrains on rear wheel drive applications. In production since 2006, it has the following ratios: 1st – 4.17, 2nd – 2.34, 3rd – 1.52, 4th – 1.14, 5th – 0.86, 6th – 0.69. Reverse gear has a ratio of 3.4 and the final drive selection will be selected from 3.15, 3.31, 3.55, 3.73 gear ratios.
The 5th generation Explorer will only have the 6-speed automatic available, mated to either a 2-liter EcoBoost inline 4 or a 3.5-liter Duratec V6.