Doosan Diesel Torque Converter – D50S D60S D70S 5-7 Ton Counterbalance

Doosan Forklift Torque Converter BSX0005683 — D50S/D60S/D70S 5-7 Ton Heavy-Duty

The BSX0005683 torque converter is the factory-spec hydraulic coupling for Doosan D50S, D60S, and D70S 5-7 ton diesel counterbalance forklifts. This unit is engineered for heavy-load material handling — ports, steel yards, lumber mills — where sustained torque multiplication under load is critical. The converter’s stall speed is calibrated to match the Doosan DB58-series diesel engine’s torque curve, ensuring the forklift can lift full-rated capacity from a dead stop without engine bogging. Unlike light-duty converters, the BSX0005683 uses a heavy-duty stator sprag clutch and reinforced lockup friction material rated for continuous operation at 5-7 ton load classes. Installing a mismatched converter on these large-frame Doosans is dangerous — incorrect stall ratio causes transmission slippage when handling near-maximum loads, leading to brake fade and load instability.

Common failure symptoms on D50S-D70S torque converters include transmission overheat warnings after 20-30 minutes of continuous operation (fluid degradation from slipping lockup clutch), metallic whine that intensifies with engine RPM (worn pump hub bearing or damaged stator one-way clutch), and shudder during acceleration from standstill with a load (glazed lockup clutch friction material). Diagnosis tip: before condemning the converter, check transmission fluid for burnt smell and metallic particles — if found, the cooler lines must be flushed or the new converter will fail within hours. The D50S/D60S/D70S transmission cooler is frame-mounted and often overlooked during converter replacement; residual debris from a failed converter circulates back and scores the new unit’s pump bushing.

Installation requires removing the transmission from the forklift — this is not an in-frame service on D50S-D70S models. Step-by-step: drain transmission fluid, disconnect cooler lines at the transmission, unbolt the flexplate access cover, remove six flexplate-to-converter bolts through the access window, support the transmission on a 2-ton transmission jack (the assembly weighs approximately 180 kg assembled), unbolt bellhousing bolts, slide transmission rearward until the converter pilot clears the crankshaft. Critical torque values: flexplate bolts 65-75 Nm (Doosan spec, cross-pattern tightening), bellhousing bolts 85-95 Nm. Replace the front pump seal, input shaft O-ring, and flexplate bolts (they are torque-to-yield and must not be reused). Fill with Doosan-approved ATF SP-III or equivalent Dexron III — capacity approximately 12-14 liters including converter fill.

This torque converter fits Doosan D50S (5-ton), D60S (6-ton), and D70S (7-ton) diesel counterbalance forklifts equipped with the DB58-series engine and powershift transmission. It does NOT fit Doosan D50SC-5 or G50S LPG models — verify your data plate for “D50S” or “D60S” or “D70S” model designation before ordering. For related Doosan drivetrain components including input shafts, clutch packs, and transmission control valves, visit our Forklift Hydraulic Transmission Parts category. OEM specifications and service manuals are available at the Doosan Industrial Forklifts official website.

Technical Specifications

Compatible Forklift Models

Each torque converter is securely packaged in a reinforced wooden crate with internal bracing to prevent damage during international freight. Standard shipping to major ports worldwide via air or sea freight. For bulk orders or technical compatibility verification, contact our team with your Doosan forklift model and serial number.