Distinction Bosch SB7 / SB23 OC / SB23 System

Here is a short guide on correctly identifying the Bosch hydraulic system of your tractor, applicable across all tractor brands and models:

Bosch SB7

The Bosch SB7 system was used by various manufacturers from around 1960 into the 1990s in different generations.

Bosch number range:

  • Control units for rear hydraulics (former designation): Hy-SR10H...
  • Control units for rear hydraulics (new designation): 0 521 704 ...
  • Additional control units (old designation): Hy-SRZ10H...
  • Auxiliary control units (new designation): 0 521 705 ...

Manufacturers who installed the system (list may be incomplete):

  • Fendt
  • MB Trac
  • Steyr
  • Porsche
  • Kramer
  • Deutz
  • Case IH (IHC)
  • Lindner
  • Schlüter
  • Güldner
  • Eicher

Flange system:

The first production years were delivered with three stud bolts (shown here as an example using a control unit):

Later model years were then delivered with four stud bolts:

Bosch SB7 Endplatte Ansicht der Flanschseite

The additional holes between the holes for the stud are for dowel pins; they serve to center the valve, but they were not always installed.

All valves with four studs are backward compatible with the three-stud version!

Note:

IHC has frequently installed SB9 valves in the tractors delivered with this system in recent generations; an additional return line is integrated into the valve here.

 

Bosch SB23 OC

The Bosch SB7 system was used by various manufacturers from around 1980 into the 2000s in different generations.

Bosch number range:

  • Additional control units: 0 521 609 ...

Manufacturers who installed the system (list may not be complete):

  • Case IH
  • Claas
  • Renault
  • Deutz
  • Steyr
  • MF
  • Zetor
  • Valtra
  • Valmet
  • Lindner

Flange system:

The system was always delivered with three stud bolts. A characteristic feature of the system is the symmetrical arrangement of the stud bolts and the supply bores:

Note!

For the original valves there is a right-hand and a left-hand version (depending on which side the valves are mounted). Replacement control units are usually made flexible for both versions here by means of a replaceable sealing plate.

 

Bosch SB23 LS

The Bosch SB7 system has been used by various manufacturers from around 1980 up to the present in several generations.

Bosch number range:

  • Zusatzsteuergeräte (older designation): 0 521 610 ...
  • EHR control unit (older designation): 0 521 220 ...
  • Additional control units & EHR control unit (new designation): R91700...

Manufacturers who install the system (list may not be complete):

  • New Holland
  • Case IH
  • Claas
  • Fendt
  • Deutz
  • MF
  • Lindner
  • McCormick
  • Stey
  • Doppstadt
  • Landini
  • JCB

Flange system:

The system was always delivered with three studs:

The two small drillings in the area of the electrical unit are used to supply the control with pilot pressure. The purely mechanical design of the SB23 LS system does not have these drillings!

Note!

For the valves there is a right-hand and a left-hand version (depending on which side the valves are mounted).

The original valves had notches in the area of the head studs. If these surfaces were machined, shims of 0.05mm must be fitted. These should prevent the valve from binding.