0985604 Original Excavator Thrust Washer for ZX650-3 ZX670-6 ZX690-5A

Part number 0985604 is usually classified as THRUST WASHER/SHIM WASHER in Hitachi's original system, and is often found in the planetary gear stage of the rotary motor reducer/final drive in the exploded view, used to control the axial clearance between the gear and the housing/bearing side. It is commonly found inside the gearbox of Hitachi's large/mining grade platforms (such as ZX650LC-3, ZX670LC-5, etc.), but the same number may correspond to different thicknesses and tolerances in different batches/gearbox versions. Therefore, do not generalize based on "looks like": ordering and receiving must be done with Hitachi EPC to lock the drawing number of the part, and check the machine model+serial number+reducer nameplate/old part engraved label to ensure that the thickness is consistent with the fitting size.

Essentially, it is a high-precision annular pressure bearing pad: installed on both sides of the planetary gear or bearing end, used to receive axial force and limit the axial displacement (end face clearance) of the gear/bearing, making the transmission more stable, noise lower, and component life longer. Original parts are mostly made of hardened steel or steel back+wear-resistant surface (if necessary, bimetallic), emphasizing flatness and surface smoothness, inner/outer diameter/thickness tolerances, and deburring of edges, so that they can withstand long-term wear and tear in gear oil baths, without "lifting" or producing metal particles. It does not adjust the flow rate on its own, but once the gap becomes too large, it will exhibit axial looseness and periodic buzzing during rotation/walking; Being too small and causing heat stagnation, therefore "original factory thickness and tolerance" is its core value.

It is a box item that is only touched during disassembly: it is not adjusted or replaced separately for daily use. The typical trigger point is to open the box and check for pitting corrosion on the tooth surface, bearing clearance, or to find that there is a "steady speed buzzing" during rotation/walking and the clearance measurement exceeds the tolerance. Thoroughly clean the joint surface and oil passage during disassembly and assembly, and do not use a grinding wheel to polish the surface; The old gasket/old position mark is for reference only. The clearance between the same group should be rechecked according to the manual using a gauge/feeler gauge. If adjustment is necessary, the selection logic of the original factory specified thickness should be followed instead of "adding an extra pad randomly". When reassembling, it is necessary to tighten the fasteners in a cross order and with the specified torque, and check the oil level/oil seal synchronously - it is more common to see the deformation of the tightening shell or the loosening causing the gap to run away, which is more common than "incorrect gasket material".