Hyundai HD78 Side PTO –Vacuum (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 device, and it can be installed beside or behind the main gearbox. Side PTO units are commonly used in heavy-duty vehicles, agricultural machinery, and industrial equipment where power needs to be delivered to multiple auxiliary systems.

1
Vehicles & Gearboxes

2
Compatible Gearbox Numbers

3
Technical Specifications

4
Mounting to Main Gearbox

5
Hydraulic Pump Coupling

6Rotation & Speed

7
Recommended Accessories

8
Warnings & Key Notes

9
FAQ

To connect the side PTO to the main gearbox, a rectangular mounting port with six bolt holes is built into the PTO housing. These holes are used for the mounting bolts and ensure a strong, secure attachment to the gearbox. This design not only simplifies installation, but also helps prevent oil leakage and protects internal components from damage.

This side PTO is specifically installed on the left side of the gearbox. The rectangular 6-bolt port is secured to the gearbox housing using appropriate bolts and washers, so the PTO remains stable and vibration-free under pump load and torque impacts. Depending on the gearbox and PTO model, you may need gaskets/shims of different thicknesses for proper sealing and accurate alignment of the mounting surfaces.

The gears inside the side PTO must be designed to mesh accurately with the main gearbox gears. The gear shape, size, and spacing are selected through engineering to ensure smooth power transfer without shock loads. In this Hyundai model, the gears are right-hand helical and relatively coarse, and they are fully enclosed inside the PTO housing.

Side PTO units can be single-gear or two-gear. In single-gear models, the gear train is arranged in one row and is typically used for lighter-duty systems with lower power demand, taking up less space. In two-gear models—such as this vacuum high-speed PTO—the gears are arranged in two separate rows. This design increases load capacity and enables higher power transfer. This type of PTO is better suited for industrial machinery and heavier vehicles and offers improved stability under demanding operating conditions.

Side PTO control systems can be manual, pneumatic, vacuum, or electric. These controls regulate power transfer, torque, and rotational speed between the main gearbox and connected equipment, and help prevent excessive load on system components. In Hyundai HD78 side PTOs, the control method is often vacuum. This system uses vacuum assistance to engage and disengage the PTO more precisely and smoothly, helping maintain gearbox stability under different operating conditions.

The pump coupling interface on this PTO is designed as a UNI output. This type of coupling makes pump installation easier and provides better compatibility with different pump types. The UNI design helps create a strong and secure connection and ensures power transfer with minimal vibration and stress.

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

1. UNI pumps: mounted directly onto the PTO.
2. ISO pumps: connected using an adapter between UNI and ISO.
3. Flange & driveshaft installation: installing a flange on the PTO output and transferring power through a driveshaft (cardan shaft).

The PTO output rotation direction depends on the gear type and internal design, and it can differ between single-gear and two-gear models:

1. Single-gear PTOs:
   Typically, the output rotation is opposite to the input rotation. If the input is clockwise, the output will be counter-clockwise (and vice versa).
2. Two-gear PTOs: Due to multi-stage gear engagement, different rotation designs are possible. In this vacuum high-speed model, the PTO output rotation is counter-clockwise (CCW). Therefore, your selected pump must be compatible with this rotation direction.

• Lever control cable: for controlling a manual PTO in hybrid setups (if used).
• Vacuum kit: for controlling a vacuum PTO and achieving smoother engagement.
• 6-spline to 4-bolt flange: for mounting a driveshaft on a UNI-output PTO.

In this article, the most common PTO model compatible with your vehicle’s gearbox is introduced; however, your vehicle may have a different gearbox installed due to custom specifications or differences in gearbox variant. To avoid any mistake in selection, be sure to write down the gearbox number from the gearbox nameplate and consult Raman Shams experts based on the gearbox serial number so the correct PTO model can be recommended.

The dump body manufacturer or the upfitting company determines which hydraulic pump and hydraulic valve are used in the system. Therefore, if you plan to install a new pump instead of the old one, it is best to have a basic understanding of dump pump types (displacement, operating speed, nominal pressure, etc.) so you can select the right model. In this article, a common configuration for your vehicle is introduced; however, it is recommended to consult Raman Shams experts before final purchase.