Lead trailer hydraulics 8

4 Hose Hydraulic

Lead trailer hydraulics 1

Tractor: Contains all control valves

  • 2 spool-open center- control valve OR (2) single spool- open center- control valves
  • (2) on/off/on momentary switches to control dump cycle – one for each unit
Lead trailer hydraulics 2


  • (2) sets of Hydraulic couplers on front nose of lead. Left side controls Lead, right side controls Pup.
  • This is a very good system to decrease troubleshooting time. No controls on the trailers. If it doesn’t work, the problem is on the tractor.

Selector Valve

Lead trailer hydraulics 3


  • (1) single spool-open center- control valve
  • (1) on/off/on momentary switch to control dump cycle
  • (1) on/off locking switch to select lead or pup
Lead trailer hydraulics 4


  • (1) set of hydraulic couplers on front nose of lead
  • Hydraulic Selector valve mounted in Lead unit
  • Selects which unit to send the pressure to- lead or pup
  • Controlled with electric switch from cab, electric over air solenoid on lead trailer
  • 7-way, 6-way or 4-way connection at front of Lead

Electric Valve w/ Power Beyond

Lead trailer hydraulics 5


  • No Control Valve on Tractor
  • (2) on/off/on momentary electric switches to control valves in trailers
Lead trailer hydraulics 6


  • Electric over air switched single spool-open center-valve with power beyond in lead unit
  • Electric over air switched single spool-open center-valve in pup unit
  • 7-way, 6-way or 4-way connection at front of lead & jumper between lead and pup
  • Bypass valve in frame of lead must be switched to circulate hydraulic oil from power beyond when pup is not hooked to lead unit

This set up minimizes the amount of valving needed on the tractor. This is useful if several different tractors will be pulling the unit.

Figure 1 - Lead Unit/Power beyond:

Lead trailer hydraulics 7
Lead trailer hydraulics 8