Cat 963 LGP track loader: prefixes and hydrostatic drive diagnosis

The original 963 and its hydrostatic drive

Cat's former-model register separates the original 963 from the 963B and 963C. The original entries carry 6Z, 11Z, 18Z and 21Z prefixes. They share the listed flywheel rating, but the approximate operating weights differ between configurations.

The French-built entries have their own prefixes and production spans. Identify the machine before borrowing a later loader's specification.

The B entry introduces a different engine and bucket reference. Later C entries change the recorded dimensions again, and the Tier 2 C entry identifies a different undercarriage arrangement. A seller's shortened description of “963 loader” cannot distinguish these machines.

Use the full prefix and the installed front equipment when looking up parts or transport dimensions.

The handbook describes approximate configured operating weights, not a scale ticket for this LGP machine. Its length note measures to the smallest general-purpose bucket. A wider shoe arrangement, another bucket or a rear attachment still needs identification.

The earlier LGP figures below remain distinct from the handbook's general former-model rows.

Two axial-piston pumps supply the original hydrostatic transmission's track motors. A common charge-and-filter problem can affect both sides. Cat's special service bulletin explains that a restricted filter sends oil back to the reservoir through the filter relief valve.

The result is reduced control supply, reduced pump displacement and brake application. Weak travel on both tracks therefore does not, by itself, establish that both motors need replacement.

The bulletin separates charge supply, underspeed control, operate/brake control, servos, drive pumps and motors, and cooling. Its two-speed motor discussion is expressly for the 973. Do not apply that section to the 963.

Unequal track response calls for a different investigation from a shared charge-supply loss. Servo linkage and synchronization belong in that diagnosis. Cat also warns that opening a dirty, undrained filter housing can introduce contamination.

Have a qualified technician use the matching service procedure and restraints; an unsupported track-drive demonstration or an adjustment copied from another prefix is not a substitute for pressure testing.