TERMINOLOGY

There are a lot of parts in a limited-slip not found in a regular differential, so we had better start off with some names and definitions for these parts.

Case

This is the big cast piece to which the ring gear bolts. It is actually two parts, the major portion of the case and an end-cap to hold all the parts in. The end cap is held on by four countersunk Phillips-head machine screws. The inside of the case has four large grooves in it that run parallel to the axle centerline. The ring gear bolts go through the end-cap and the case and are threaded into the ring gear.

Side Gears

The side gears in the LSD are a bit different from regular side gears but they do the same thing. They have a splined hole in the middle that mates with the splined ends on the axles. They also have a "shoulder" on the back side (away from the teeth) that has six grooves or notches parallel to the axle centerline. The tabs on the Friction Disks and Spring Disks fit into these notches.

Pressure Rings

These are two large cast pieces that sit inside the case. They have four tab-type protrusions around the outside that fit into the grooves in the case. They also have v-shaped slots where the ends of the Pinion Shaft sit.

Pinion Shaft

This is the pivot shaft for the pinion gears. The middle part of the Pinion Shaft is flat on two sides. The pinion gears sit on the round portion. It is different from a regular pinion shaft in that the ends have flat areas machined on them in a v-shape. These flats sit in corresponding notches in the Pressure Rings.

Pinion Gears

These do very much the same thing as regular pinion gears. They pivot on the pinion shaft and sit between the side gears. In a regular differential they are also referred to as "spider gears."

Friction Disks

These are round flat ring-like steel disks that go inside the case.The disks have 6 round tabs towards the inside that fit into the grooves in the back of the side gear. They come in several thicknesses, 1.75 mm, 1.85 mm. and 2.00 mm being the most common.

Friction Plates

These look very much like the Friction Disks, except that they have four round tabs towards the outside. These tabs fit into the grooves inside the case. The plates come in the same thicknesses as the Friction Disks.

Spring Disks and Spring Plates

Some LSD units have these and some do not. They are like the Friction Disks and Friction Plates except that they are dished instead of flat. The technical name for this is a Belleville spring. I believe their purpose is to give the LSD a more progressive action.

"The Stack"

This is how the plates and discs look when they are assembled onto the back side of the side gear. You can see how they alternate, how the tabs on the plates line up with the tabs on the pressure ring and how the tabs on the discs line up with the slots in the side gear.