Remove all the electrical [1] and pneumatic [2] connections from the gearbox assembly. Put labels on all cables and hoses to identify their connection points.

Record the wiring configuration for the spindle motor [3]. Disconnect the wires. Remove the tool release piston (TRP) [4]. If the machine has through-spindle coolant (TSC), disconnect the plumbing as necessary.

If the gearbox has a mid belt shield [5], remove it.

Remove (5) of the (6) bolts from the gearbox assembly. Keep (1) of the bolts [8] toward the rear of the machine. Loosen the (1) remaining bolt. With your hands, pull the gearbox toward the spindle. This loosens the tension on the spindle belts [6]. Connect the hoist to the gearbox [7]. Raise the hoist enough to support the gearbox. Remove the last bolt from the gearbox assembly. Slowly raise the gearbox.

Make sure no cables are connected to the gearbox. Remove the gearbox from the machine.

Remove these parts and put them on the new gearbox:

• Transmission oil pump [1]
• Air solenoid assembly [2]
• Spindle Encoder [3] (see step 4)
• Spindle drive belts [4]. Replace the belts if necessary.
• High/low gear sensors or switches [5]
• Shot pin orientation assembly (only on machines with a brush motor)

If your old gearbox had Mechanical Switches [6], you must remove the gearbox shift dampener [9] from the new gearbox. Do these steps:

1. Remove the (4) bolts [8] from the oil tank [7].
2. Remove the shift dampener [9]. Transfer the mechanical switches [10] to the new gearbox.

If the encoder from the old gearbox is a belted encoder [2], do these steps:

1. Remove the belted encoder [2] from the old gearbox..
2. Install the belted encoder assembly [2] onto the standoffs [1].

If the encoder from the old gearbox is not a belted encoder [2], remove the standoffs [1]. Move the encoder to the new gearbox.

If the machine has an air regulator assembly:

1. Remove the 35-psi air regulator [3] from the input of the shift solenoid. 
2. Replace the 35-psi air regulator [3] with the tee fitting [4].

Install the fitting [5] on the high-gear side of the air solenoid assembly. Connect the hose [6] from the air-over-oil shifting assembly to the fitting [5]. Do not test the solenoids until after you have completed the gearbox replacement procedure.