Hyundai HD78 Side PTO – Manual (High-Speed)

A side PTO is one of the key components in the power transmission system of vehicles and industrial machinery. It is typically used to transfer engine/gearbox power to other parts of a vehicle or equipment, and it can be installed on the side or rear of the main gearbox.
Side PTO units are especially common in heavy-duty vehicles, light trucks, agricultural machinery, and industrial equipment where power needs to be delivered to multiple auxiliary systems.

To mount the side PTO to the main gearbox, a dedicated port is designed on the PTO housing. This port is rectangular and features six bolt holes. These holes are used for mounting bolts and ensure the PTO is attached firmly and safely to the main gearbox. In addition to strength, this design helps prevent oil leaks and protects internal components from damage.

This side PTO is specifically installed on the left side of the gearbox. The mounting interface is provided through the rectangular six-bolt opening on the main gearbox housing. Suitable bolts and washers keep the PTO stable and vibration-free under operating stresses and transmitted torque.

Required parts:

Depending on your gearbox and PTO model, you may need gaskets/shims of different thicknesses to ensure proper sealing and accurate alignment of the mounting surfaces.

The gears inside the side PTO must be designed to mesh precisely with the main gearbox gears. In this model, the gear geometry and spacing are engineered to provide smooth engagement and uniform load distribution without shock.
The gears in this Hyundai HD78 side PTO are right-hand helical and relatively coarse, and they are fully housed inside the PTO casing.

Side PTOs can be single-gear or two-gear units. In single-gear models, the gear train follows a single path and is typically used for lighter-duty systems with lower power demand. This design is more compact and suitable for general applications and light loads.

In two-gear models—which can also be used with this type of PTO—the gear train runs in two separate stages, providing higher load capacity and greater power transfer capability. This type is preferred for higher-pressure and higher-torque systems such as industrial machinery and heavy-duty vehicles, offering improved stability under demanding operating conditions.

Side PTO control systems can be manual, pneumatic, cable (push-pull), or electric to suit different operating conditions. These systems engage/disengage the PTO and manage the transmission of power and torque.

For the Hyundai HD78 side PTO discussed here, the control type is manual. This design allows the operator to engage or disengage the PTO mechanically and reliably, ensuring accurate power delivery to the pump or other driven equipment.

The pump coupling interface on this PTO is designed as a UNI output. This design simplifies installation, improves alignment, and increases connection rigidity between the PTO shaft and the pump shaft—helping ensure optimal hydraulic system performance.

Depending on the pump configuration, this connection can be implemented in three ways:

1. UNI pumps: which connect directly and very easily to the PTO.
2. ISO pumps: which require a suitable adapter between UNI and ISO.
3. Flange & driveshaft installation: installing a flange on the PTO output and transferring power via a driveshaft (cardan shaft).

The PTO output rotation direction depends on the internal design and the number of gear stages, and it may differ between models.

1. Single-gear PTOs:
   In this type, the output rotation is usually opposite to the input rotation. If the input is clockwise, the output is typically counter-clockwise (and vice versa).
2. Two-gear PTOs:
   Due to multi-stage gear engagement, the output rotation may vary depending on the internal design.
   In the HD78 manual high-speed model, the PTO output rotation is counter-clockwise, and it must match the rotation direction of your selected pump.

• Lever control cable: for engaging/disengaging the manual PTO from inside the cabin.
• Vacuum assist: in some cases used to help achieve smoother engagement for manual PTOs.
• 6-spline to 4-bolt flange: for mounting a driveshaft on a UNI-output PTO.

This article introduces the most common side PTO model available on the market for your vehicle’s gearbox; however, your vehicle may have a different gearbox installed due to custom orders or previous modifications. To avoid any mistake in selection, be sure to note the gearbox number from its nameplate and consult Raman Shams experts based on the serial number so the correct PTO can be identified for you.

The dump body manufacturer or the upfitting company selects the type of hydraulic pump and valve used in each dump system. If you plan to replace an old pump with a new one, it is best to first gain a basic understanding of dump hydraulic pumps (displacement, operating speed, working pressure, etc.) to select the correct model.
This article introduces a common configuration for the Hyundai HD78; however, it is recommended to consult Raman Shams experts before making a final purchase.