Que.  What is the meaning of "ZF"?
Ans. "ZF" stands for the German word "ZAHNRADFABRIK", which means "Toothed Wheel (Gear) for Zahnrad, and manufacturing for Fabrik, that is "Gear Manufacturer".
The company is based in Friedrichshafen-Germany, and hence known as "ZF Friedrichshafen".
The company manufactures Drive line and Chassis related parts and are World leaders.
Que.   What is the meaning of "ZFLS"?
Ans. "ZFLS" stands for the German word "ZAHNRAD FABRIK LENKSYSTEME", which is a Division of Zahnradfabrik Friedrichshafen. Since 1990 it is a 50:50, Joint Venture Company between "ZF Friedrichshafen" and "Robert Bosch" and manufacturing Steering Systems.
Que.   What is the meaning of "ZFI"?
Ans.  ZFI is the short form for the Indian company "ZF Steering Gear (India) Ltd.", established in 1982. Earlier to 1990 it was a joint venture company between ZF Germany and since 1990 a joint venture company with "ZFLS". The company is situated in the eastern part of Pune, and is 27 Kms. From Pune station on the Pune ‚ÄďAhmednagar High-way. It is about 200 kms. south of Mumbai.
Que.   What is the difference between
a) Manual (Mechanical) Steering and
b) Power Assisted Steering System (PAS) and
c) Fully Assisted Power Steering System?
Ans. a) Manual Steering Systems are operated entirely with the Human Muscle Power, with the "Mechanical Advantage".

b) Power Assisted Steering Systems are supported with external energy, along with the Human muscle power. This Power can be generated by Hydraulics, Pneumatics Or Electrical energy, which is produced basically from the Vehicles Engine. Also, the vehicle should be Steerable in absence of the external Power.

c) Fully Assisted Steering Systems or Hydrostatic/Servostatic Steering Systems operate completely with Hydraulic Power. This system does not have any mechanical linkage between the Steered wheels and the Steering Systems hence are basically used on heavy and slow moving vehicles like Fork Lifts/Cranes etc. These Vehicles cannot be steered in absence of the External Power.
Que.   How does the ZF Hydraulic Steering System operate?
Ans. The ZF Steering System consists of Oil Reservoir, Steering Pump and the Steering Gear. These are connected by Rubber and Metal Hoses by the Vehicle Manufacturers.
The system is filled with a special Steering Oil known as ATF. The Oil Reservoir acts as an Oil Storage and filtering unit.
The Pump is connected to the Engine Pulley/ Gear or Coupling drive and supplies the Oil to the Steering Gear Box. When the Steering wheel is rotated by the driver, it signals the direction of movement and the requirement of Pressure to a Valve in the Steering gear Box. Based on this input, Oil pressure is generated in the Steering Gear Box and gives the required force/ power to the System. The Driver has to apply only 5 to 10 % of the Force required and the balance Force is provided by the Oil Pressure.
Que.   Can the Steering Oil be replaced with any other medium or Oil?
Ans. The Pump uses the same Oil for its internal Lubrication and pressurizing the System. Also, it needs to be free of Air and should not damage the Seals and O-Rings in the System. Hence special Oil "ATF" (Automatic Transmission Fluid) is to be used.
Que.   When is this Oil to be replaced?
Ans. The Oil is to be replaced as per the recommendations of the Vehicle manufacturers, to coincide with the other Service Schedule. Normally the Oil should be replaced between 50,000 to 100,000 Kms of vehicle running. The Filter is also to be replaced during this time. It is also advisable to change the Oil and filter in the System if any major repair is done on the Steering Gear Box or Steering Pump.
Que.   Is it required to top up the Oil after running the Vehicle for some time?
Ans. Normally there is no topping- up of Oil required. But we recommend checking of the Oil level at regular intervals of 5,000 Kms This is to ensure that no leakage of Oil is taking place. Leakage/Seepage of Oil should be immediately attended to.
Que.   What is the reason for the Oil to be foamy?
Ans. . Foaming of Oil is indication of Air in the System. Sometimes this is accompanied with Pump noise and over flowing of the Oil from the Oil Reservoir Cover when the Engine is stopped. The Suction Line is to be tightened properly to ensure no Air enters the System through Adopters or Connectors. As this is a suction line normally no Oil leakage is noticed on the Suction side i.e. the connection between the Oil Reservoir and Pump. Seepage or wetness on this lineis also not permissible.
Que.   How is the Air to be removed from the System?
Ans. The ZF Steering System is fitted with Automatic Bleeder Valves. These Bleeders remove any residual air in the system after the Commissioning of the Steering System.
Que.   What is the meaning of Commissioning of the Steering System?
Ans. Commissioning of the Steering System means Oil Filling, Bleeding and Limiter Setting, of a Vehicle after the Steering System is fitted. While commissioning, that is Oil filling in the System, it is recommended to Jack up the Vehicle. Open the oil Reservoir Cover completely and pour oil till the top of the Oil Tank. The Engine should then be cranked to allow the Oil to flow down in the System. Care is to be taken that there is always Oil in the Tank.
Once the Oil level has become stable, the Engine can than be started and kept in idling condition for some time.
The Steering wheel then can be rotated from lock to lock ends, till the Oil level is stable and no Air bubbles are formed.
The engine should be stopped and Oil Level checked, if the Oil level rises more than 20 to 30 mm. And the Oil is foamy, the above procedure should be repeated.
When the Steering Wheel is taken to the lock positions i.e. extreme turns on the Left and Right side, the pressure in the system should be 30 to 35 bar in the Steering Gear model i.e. 8043 and 8033 models.
The Jacks from the Front axle of the vehicle than can be removed.
Que.   What are Hydraulic Limiters?
Ans. Hydraulic Limiters are Adjustable type Pressure Relief Valves, fitted in the Steering Gear boxes of HCV/MCV/LCV type of Vehicles. These are "Adjustable" type (Model 8043 fitted on HCV/MCV type of Vehicles) and "Non Adjustable" type (Model 8033 fitted on LCV type of vehicles). The SUV/MUV vehicles do not require this feature. (Model M033). In driving condition of the vehicle, when a Driver takes extreme lock turns to the right or left, the vehicle is considerably slow and the System pressure may shoot upto its maximum when the Axle stops are reached. Higher pressure in the system may loads the Engine, causing extra power consumption, load on the Pulley/Belt and higher torques on the Steering linkages. To avoid this, the Hydraulic limiters are provided and are to be adjusted to offload when the Axle Stops are reached.
Que.   How are the Hydraulic Limiters set?
Ans. Generally, the limiters for the first time are to be set by the Vehicle Manufacturers, depending on the wheel lock/stopper angles. If this is to be reset for some other reason on a vehicle, please contact ZF representative or ZASS.