The Difference Between EquaLok and TractionLok Rear Axles

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Image: Limited Slip Differential

Ford Limited Slip Differential

Ford's limited slip differential or rear axles changed names over the years, as well as design. Both do the same thing, but go about it in different ways.

The EquaLok rear axle design is older than TractionLok, and uses a belleville spring to tension the clutch pack. This design is somewhat compromised, as the tension is always constant, and is always the same, regardless of operating conditions. It has to strike a fine balance, as too much tension wouldn't allow it to slip when turning corners, and not enough tension would cause it to be too loose for hard acceleration and traction when needed.

TractionLok is a torque-sensitive design that uses four coil springs that keep a constant tension on the clutch pack, but this tension is not very tight and is designed for light loads, such as driving on wet streets or on snow. The tooth design of the differential pinion is different from EquaLok, and was designed to put side loads on the side axle differential gear, which is connected to the clutch plates, which compresses the clutch pack and causes it to lock up. This design provided light locking for normal driving and increasingly firmer lockup for higher loads.

Both axles used an alternating series of steel plates and paper-lined plates, similar to those found in the clutch packs of automatic transmissions. Some TractionLok axles used all metal plates with grooved and serrated plates, a design somewhat like that of GM's PosiTraction units, which is why the axle lube specified by Ford for use in the more recent TractionLok axles (1980's-1990's) didn't work well in the older ones. The clutch plate design and composition of the materials used was different.

To rebuild a worn out TractionLok axle, a special tool is required to determine the proper shim thickness behind the clutch plates for correct tension specifications. It's important that the proper shims are used, as just installing a clutch pack without the proper shimming can cause it to be too tight or too loose, providing unacceptable performance from the axle.