Transmission Parts FAQ

Transmission identification requires finding the metal ID tag — but location varies by brand:

• HOWO/SINOTRUK manual (HW19710, HW19712, HW20716): ID tag riveted to the LEFT side of the gearbox case, near the clutch housing flange. Look for the full model designation: e.g., HW19710 is the 10-speed manual, HW19712 is 12-speed with overdrive.
• ZF power-shift (4WG-210, 4WG-260, 6WG-310): ID plate on the TOP of the converter housing. The model is stamped as: ZF 4WG-210. Also note the serial number — internal design revisions (index A/B/C) affect parts fitment.
• LIUGONG/SANY wheel loader transmission: Often a ZF-licensed design produced in China. Look for the ID plate near the shift control valve body. The format is typically BS305 or YJ315 (Chinese designation) with a ZF cross-reference on the plate.

If the tag is missing: Count the number of shift lever positions, measure the bell housing bolt pattern, and photograph the transmission from 3 angles. We can identify it from photos with ~90% accuracy. Send us your photos and we'll ID it free of charge.

Clutch pack failure symptoms depend on transmission type:

Manual transmission (HOWO HW19710/HW20716):

• Grinding when shifting into a specific gear → worn synchronizer ring for that gear pair. Replace the synchro ring + cone.
• Clutch pedal feels spongy or engages at the very top → worn clutch disc (friction material thickness below 2mm). Replace clutch disc + pressure plate + release bearing as a set.
• Transmission pops out of gear under load → worn shift fork pads, detent spring, or synchronizer hub. Inspect all three.

Power-shift transmission (ZF 4WG, wheel loader type):

• Sluggish engagement or delayed shift → worn clutch piston seals (internal leakage). Pressure test each clutch circuit — if pressure drops >15% from spec, rebuild that clutch pack.
• Burnt-smelling transmission oil → slipping clutch pack generating excessive heat. Drain oil and check for friction material particles (dark, fibrous debris).
• Machine won't move in forward but moves in reverse (or vice versa) → specific directional clutch pack failure. ZF 4WG has separate forward and reverse clutch packs — replace the affected clutch friction discs + steel separator plates.

Contact us with your transmission model and symptoms — we'll help you identify which clutch pack kit you need.

For ZF transmissions (4WG-210, 6WG-310) used in Chinese wheel loaders, here's the real price comparison:

• Genuine ZF clutch pack kit (frictions + steels): $800–1,200 per clutch pack. Full transmission rebuild kit (all frictions, steels, seals, gaskets): $3,500–5,000.
• OEM-equivalent (ZF-licensed factory in China): $500–750 per clutch pack. Full rebuild kit: $2,200–3,200. Same friction material spec (paper-based, sintered bronze for high-energy packs). We've supplied these to mining operations running 2,000+ hours without issue.
• Generic aftermarket: $200–400 per clutch pack. Not recommended. We've seen generic frictions delaminate at 300 hours in mining applications. The cost of a second teardown far exceeds the initial savings.

Our recommendation: For mining and heavy-duty applications (wheel loaders in quarry, bulldozer in rock) → OEM-equivalent minimum. For light-duty (loader-backhoe, telehandler) → quality aftermarket from known manufacturers (Allison-licensed, etc.) is acceptable for auxiliary clutch packs only. Never use aftermarket on the main directional clutch.

Transmission service intervals vary by type and duty cycle:

• HOWO manual transmission (HW19710/HW20716): Oil change every 50,000 km or 1,000 hours (whichever comes first). Oil type: SAE 80W-90 GL-5 gear oil. Capacity: 14–16 liters.
• ZF 4WG power-shift (wheel loaders): Oil + filter change every 1,000 hours (standard duty) or 500 hours (mining/heavy dust). Oil type: SAE 10W hydraulic/transmission fluid (meeting ZF TE-ML 03 spec). Critical: use ONLY ZF-approved fluid — wrong fluid causes clutch pack glazing.
• Torque converter: Drain converter separately (has its own drain plug). Converter holds 30-40% of total system oil. If you only drain the sump, you leave dirty oil in the converter — which contaminates fresh oil immediately.

Warning sign: If the transmission oil smells burnt and appears dark brown instead of clear red/amber, you're already experiencing clutch slippage. Change oil immediately and inspect filter element for metal particles. Metal in the filter = rebuild needed.

Yes — and for older machines, a remanufactured transmission is often the most cost-effective solution. Here's the decision framework:

• When to rebuild: Machine is 3–7 years old, transmission core is undamaged (no cracked case, no bearing journal damage). Rebuild cost: 40-60% of new. Turnaround: 5–10 days (in-country) or 3–4 weeks (imported reman unit).
• When to replace with new: Machine is under 3 years old (warranty/insurance requirement), or the transmission case is cracked, or the machine generates >$2,000/day revenue (downtime cost exceeds savings from rebuild).
• When to buy used (junkyard): Machine is 10+ years old, resale value is low, and the machine runs <500 hours/year. Risk: no warranty, unknown internal condition. Only consider if the seller provides oil analysis report from the donor machine.

Our service: We supply complete remanufactured ZF 4WG and HOWO HW19710 transmissions, dyno-tested with 6-month warranty. Price typically 45-55% of new. Request a reman quote with your transmission model.

Gear grinding and pop-out are two distinct problems with different root causes:

Gear grinding (when shifting):

1. Worn synchronizer ring — The brass synchro ring has cone-shaped friction surface that wears over time. When worn, it can't match gear speeds before engagement → grinding. Replace the synchro ring for the affected gear pair.
2. Clutch not fully disengaging — If it grinds in ALL gears, not just one, the clutch is dragging. Causes: low clutch fluid (hydraulic clutch), air in clutch line, worn clutch master/slave cylinder, or bent clutch disc.
3. Wrong gear oil — GL-5 gear oil with excessive sulfur additives attacks the synchro ring brass material. Use only oil meeting the transmission manufacturer's specification.

Popping out of gear:

1. Worn shift fork pads — The nylon/brass pad on the shift fork wears, preventing full gear engagement. Replace fork pads — the cheapest fix.
2. Weak detent spring — The spring-loaded ball that holds the shift rail in position. Fatigue over time → replace detent spring + ball.
3. Worn synchronizer hub or slider — The engagement teeth on the hub/slider are rounded off → replace synchronizer assembly for that gear.
4. Worn input shaft bearing — Excessive shaft end play allows gears to walk apart under load. Replace bearing + check preload.

Diagnostic sequence: Check clutch disengagement first (free). If only 1-2 gears affected → synchro. If all gears → oil or clutch. If only under load → bearings.

Transmission internals have the most complex part numbering system in any vehicle system. Here's how to get it right:

1. Use the transmission EPC (Electronic Parts Catalog) — Each transmission has a factory parts book with exploded diagrams. For ZF transmissions, the ZF Aftermarket Portal provides free online catalogs. For HOWO transmissions, SINOTRUK's EPC system is available through dealers.
2. Provide the transmission serial number — Not just the model. A HW19710 made in 2018 may have different internal parts than one made in 2022 (mid-life improvements). The serial number locks in the exact production configuration.
3. Photograph the damaged part — Gears and shafts often have the part number stamped or engraved on them. Even if partially worn, send a photo — we can often identify it from tooth count and profile.
4. Count the teeth — If the part number is completely unreadable, count the number of teeth on the gear. Combined with the gear's position in the transmission (countershaft 3rd gear, mainshaft 1st gear, etc.), this is often enough to identify the correct part.

We do this daily: Send us your transmission model, serial number, and photos of the damaged part. We'll identify the correct OEM part number and quote within 24 hours. Start your parts request here.