Marcos Thadeu Lobo
Mechanical Engineer Graduated from the State University of Campinas (Unicamp). He is currently an Associate Consultant at QU4TTUOR CONSULTORIA [/ vc_column_text] [/ vc_column] [/ vc_row]
Self blocking differentials
Self blocking differentials – Some mobile equipment has axles with a “self-blocking” or “Limited Slip” differential system. When a vehicle makes a curve, the wheel on the outside of the curve travels a greater distance than the wheel on the inside. If the wheels were connected via a rigid axle, it would be necessary for one of them to slip, to compensate for the difference in path. The differential connects the two semi-shafts, allowing the difference in rotation between the wheels.
Figures 1/2 – Differential system: compensates for the difference in speed between wheels.
However, if one of the wheels is unable to turn or is on a smooth surface, all the engine effort will be directed to the wheel subjected to less effort, which will turn freely, making it difficult to move the equipment. Blocking one of the semi-shafts, eliminating the compensating effect of the differential, will cause the axles to have equal rotations and one of the wheels will not be turning freely.
Images 3/4 – Self-blocking differential or Limited Slip prevents free wheel rotation under less effort.
However, if equipment that has “self-locking” or “Limited Slip” differentials uses lubricating oils with API GL-5 additives, only without the proper “Limited Slip – LS” additives will noise, vibrations and possible catastrophic failure of the differential appear. So that this does not happen, the product must, in addition to complying with the API GL-5 performance level, have an additional additive that modifies friction or “Limited Slip – LS”. In service manuals for mobile assets that require this type of product, there is usually the indication “use API GL 5 LS product”.
Figures 5/6 – Various types of mobile equipment require lubricating oils for differentials with “Limited Slip – LS” additives.
With a view to savings, product standardization or difficulty in acquiring the right product, some users use lubricating oils for use in “self-locking” or “Limited Slip” differentials without the appropriate additives, which results in costly unavailability of mobile and unnecessary assets expenses with corrective maintenance.
