Setting the Scene
- TRW has been in the commercial braking and S&S business since 1906
- The company manufactures a range of over 700 matching OE quality, Proequip branded, steering and suspension parts, an all makes brake pad programme and recently introduced shock absorber programme
- In house manufacturing is carried out at five dedicated OE and aftermarket manufacturing facilities across Europe
- The programme is supplied from TRW’s new state of the art warehouse in Uberherrn, Germany.
- As a world leader in this field, with all its products tested to the extreme in laboratory conditions and on the road before they go to market, TRW’s by-word is safety.
How to inspect drag links and tie rods on HCV’s
This article illustrates what to look for in a garage when inspecting drag links and tie rods on commercial vehicles. This article should be viewed as a guide only.
Checking the ball joints
Vehicle Condition – ready to be driven and loaded! The axle to be tested may not be relieved.
Preparations – clean joint, including sealing bellows and connecting parts. Do not use cleaning agents or solvents. Use a dry cloth or cleaning rag instead. Do not damage the bellows!
Visual Check
Corrosion
Housing, shaft and cover must be free of deep corrosion pits (up to about 1mm depth allowed). It is particularly important to check the rolled edge at the side of the cover. Renew joint or steering/tie rod if the result is not satisfactory. The contact and joint surface of the counterpeice (e.g. steering/track arm eye) must be cleaned from corrosion.
Bellows
Deform the bellows by hand (massage) and check that no grease escapes from the bellows wall. Grease is only allowed to escape from the bellows opening. In addition, carry out a precise visual check of the surface. There must be no indication of holes, tears or chafe marks. Damaged bellows may cause ad hoc failure of the joint due to possible influx of water into the joint.
Renew joint or steering/tie rod if the results are not satisfactory.
Clamping Ring and Clamp Collar
Clamping rings and clamp collars press the bellows for sealing purposes against the housing or the pin.
These must lie concentrically on the plane of the countergroove. It must not be possible to rotate the bellows on the housing using manual force (do not use tools!). To this purpose, the bellow is held in the area of the clamping ring or clamp collar at the housing and an attempt is made to rotate it. Renew joint or steering/tie rod if the result is not satisfactory.
Self-locking nut
The self-locking nut must be properly fixed. The screw connection to the pin attachment must be checked for proper positioning.
Checking the matched bearings for signs of wear
Turn the steering wheel (with loaded axle) to the right and left alternatively until the front wheels move.
JOINT DESIGN COMPONENT GROUP –31-
During this process spring deflection of the ball pivot against the housing may not exceed 2.0mm axially.
JOINT DESIGN COMPONENT GROUP –33 (X-CAP)
During this process spring deflection of the ball pivot against the housing may not exceed 0.5mm axially.
In borderline cases, this path must be checked using an appropriate measuring device (e.g. caliper gauge).
The radial play is difficult to measure in the vehicle. TRW has the possibility to measure such data in special cases with a special device. As a rule the measurement of the radial play is not necessary. If the axial play is ok, the radial play is in the specified tolerance range.
CHECKING THE SCREW CONNECTIONS WITH THE DRAG LINKS AND TIE ROD TUBE
Visual check of the clamping screw connection including precision adjustment piece
The clamping screw must be properly fixed. The nut must be fitted firmly against the clamp. The screw may not be visibly bent.
Localised corrosion of more than 1.0 mm depth may not be visible at screw, nut and clamp or precision adjustment piece. If the clamp, precision or adjustment piece or the joint are not firmly fixed, premature damage to the thread may be expected. Renew joint or steering/tie rod if the result is not satisfactory.
If the clamp or clamping screw is stuck to the nut and strong corrosion is detected, these parts must be replaced.
Screw the connections with the precision adjustment piece/tube
Turn the steering wheel to the right and left alternatively until the front wheels move and check (e.g. using finger), whether the thread moves in the precision adjustment piece/tube.
If movement is detected this means that premature damage to the thread can also be expected. The steering rod/tie rod should be replaced if the results are not satisfactory.
Checking the tube
Check the tube visually for damage. If deformation due to force has been detected, replace the steering/tie rod.
