By Primary Mover
A compatible single-acting dump power unit can operate a double-acting hydraulic trailer jack with an X-Block adapter and suitable reservoir return connection. A selector valve chooses the dump or jack circuit. The X-Block chooses jack extension or retraction. In this arrangement, the existing power unit’s UP button runs the pump for both jack directions.
If your trailer already has a power-up/gravity-down dump system, adding a hydraulic jack does not automatically require a second power unit. The important questions are how to send pressure to either side of the jack, return displaced oil to the reservoir and control the supported load. This guide explains the X-Block arrangement and which components to order.
Why a double-acting jack needs directional control
A conventional single-acting dump system supplies pressure for raising the dump body. Lowering allows oil to return while gravity moves the body. That arrangement alone does not provide powered hydraulic movement in both directions at a double-acting jack.
A double-acting jack extends when pressure is supplied to one cylinder side and retracts when pressure is supplied to the other. Oil displaced from the opposite side needs a suitable return path. The X-Block adds manual directional routing for that jack circuit; it does not change the motor’s horsepower or increase the existing pump’s maximum flow.
For a compatible installation, purchase the Primary Mover jack-only option and the appropriate X-Block Poly Tank or Steel Tank Kit . The complete hookup kit contains the adapter and listed connection components. A bare adapter is a different purchase and does not supply the full hookup package.
The selector valve and X-Block have separate functions
| Component | Function |
|---|---|
| Existing hydraulic power unit | Runs the pump and supplies pressurized oil within its rated limits. |
| Manual selector valve | Selects the existing dump circuit or the added jack circuit. Operate one selected circuit at a time. |
| X-Block directional valve | Selects which jack cylinder side receives pressure and which side returns oil. |
| Reservoir return connection | Routes displaced oil back to the reservoir through a suitable return path. |
| Jack counterbalance valves | Provide load holding and control of load-driven movement. The X-Block does not replace them. |
The selector chooses which function you operate. The X-Block chooses which direction the jack moves. These are separate decisions, so a selector valve by itself does not create the full directional-control arrangement needed for this application.
How the jack extends and retracts using the UP button
With the intended circuit installed and both directions identified, operation follows this sequence:
- Stop the pump and select the jack circuit on the manual selector valve.
- Set the X-Block directional valve for jack extension.
- Use the power unit’s UP button to run the pump and extend the jack.
- Release UP and stop the pump before changing the directional valve position.
- Select jack retraction, then use UP again to run the pump and retract the leg.
- Stop the pump before returning the selector to the dump circuit.
The DOWN button is not the powered-retraction control for this X-Block arrangement. The manual directional valve changes the oil path; the UP button runs the pump for either movement. Installed hose routing determines the valve positions for extension and retraction. Follow the installation instructions and confirm the directions before applying a load.
Which X-Block kit should you buy?
The Poly Tank and Steel Tank X-Block kits use the same adapter, selector and listed hoses. Their supplied reservoir-return fittings differ. Select the kit by the actual return connection on your power unit, rather than assuming every reservoir of a particular material has the same port.
| Kit option | Supplied tank-return fitting |
|---|---|
| Poly Tank Kit | 3/4-inch NPT to 3/8-inch JIC |
| Steel Tank Kit | 1/4-inch NPT to 3/8-inch JIC |
A suitable return connection may be located on the reservoir or on the power-unit assembly where the port routes oil back into the reservoir. An unused hydraulic port is not automatically a suitable return port. Send us photos if you need help identifying the connection.
For the intended compatible single-jack installation, the complete kit provides the X-Block, selector valve, connection and return hoses, two 72-inch jack hoses, jack fittings and the selected return fitting. The hydraulic jack and existing power unit are separate. Check the current X-Block kit listing for the complete component list and installation requirements.
Why we recommend dual counterbalance valves
Directing oil into and out of a cylinder is only part of operating a loaded jack. The circuit also needs appropriate control when the trailer’s weight tries to drive cylinder movement.
Dual counterbalance valves provide load-control functions on both sides of the jack cylinder. They help hold the leg extended under the supported load and retracted while stowed. During operation, they control outgoing oil to help resist load-driven movement.
The X-Block routes flow; the jack’s counterbalance valves control the load. Pairing the adapter with a jack that has suitable load control is an important part of the complete installation. Our recommended pairing is the compatible Primary Mover jack with dual counterbalance valves.
Read why dual counterbalance valves matter on hydraulic trailer jacks , including the difference between a counterbalance valve and a basic load-holding check arrangement.
Check the complete installation before ordering
- Hydraulic circuit: confirm a compatible single-acting, power-up/gravity-down system.
- Operating limits: match pressure and flow to the jack, adapter, hoses and valves. Stay within the lowest applicable component limit.
- Reservoir: confirm adequate oil supply and an appropriate return connection.
- Hose reach: account for routing, movement, bends and protected placement.
- Mounting: match bolt-on or weld-on dimensions, structural support, lifting reach and stowed ground clearance.
- Two-jack systems: obtain a suitable dual-jack circuit and flow-distribution arrangement; the standard single-jack hookup kit does not establish a complete two-jack installation.
If you already have a compatible double-acting power unit, a standard single-jack Add-On Kit or suitable dual-jack Add-On Kit may be the appropriate starting point. If you need a new power unit, compare the complete powered kits through our Jack Kit Selector .
Single-acting pump and double-acting jack questions
Do I have to replace my existing dump power unit?
Not necessarily. A compatible existing single-acting power unit can supply the X-Block circuit. Confirm its condition, hydraulic specifications, oil supply and return connection before choosing the installation.
Does the X-Block increase lifting capacity or operating speed?
No. It adds directional routing. Available flow, operating pressure, cylinder dimensions and the rest of the system still determine performance. If you need a new power unit, compare our separate double-acting power-unit options .
Can I use the dump body and hydraulic jack simultaneously?
No. This manual-selector arrangement selects one circuit at a time. Stop the pump before changing the selector position.
Does the X-Block kit include the hydraulic jack?
No. Choose the jack-only listing separately. The complete X-Block hookup kit also does not include a power unit or reservoir.
Can I use it on a telescopic dump-trailer system?
A compatible power-up/gravity-down telescopic dump system may be a suitable application. The power unit, return connection, pressure limits and added jack circuit still need to be checked.
Get help choosing the correct jack hookup
Compare hydraulic trailer jacks and kits or contact Primary Mover with photos of your power unit, available return ports and trailer mounting area. Call 985-888-6554 or email sales@primarymover.com.