Your Bukhanka’s gearbox and transfer case are the core of the driveline. Smooth shifting, quiet operation and long service life depend on clean, correct oil. Russian owners often say: “A UAZ will limp on bad engine oil longer than on bad gearbox oil.” Below is a combined, field‑tested guide for both components, based on workshop steps and years of Eastern European off‑road experience.
Why these oil changes matter
- High loads & heat: Gears, bearings and (in the gearbox) brass synchros depend on proper EP additives and clean viscosity.
- Water/mud ingress: After river crossings oil can turn milky—lubrication collapses and wear accelerates. Change immediately if cloudy.
Recommended oils
- Gearbox: GL‑4 only (safe for yellow‑metal synchros). 75W‑90 synthetic for cold climates; 80W‑90 mineral for hot/heavy use. Capacity ~1.5–1.7 L.
- Transfer case: GL‑4 or GL‑5 (no synchros). Many owners keep the same oil as the gearbox for simplicity; some prefer GL‑5 for extra EP. Capacity ~0.9–1.0 L.
⚠️ Do not fill the gearbox with generic GL‑5. Unless the product is explicitly “yellow‑metal safe”, Russian forum reports link GL‑5 to synchro corrosion and poor shifting.
Service intervals
- Factory: every 35,000–40,000 km or 2 years.
- Off‑road / water use: every 15,000–20,000 km or immediately after deep crossings.
- Condition‑based: burnt smell, metallic glitter, or cloudy oil = change now.
Tools & materials
- 12 mm square drive key (typical for gearbox & transfer case plugs).
- Drain pan, rags, brake cleaner; new sealing washers.
- Oil pump/syringe (fill points are awkward).
- ~3 litres of GL‑4 (to service both units with margin).
Procedure (both units)
- 1) Warm up: Drive 5–10 km, shifting through all gears. Engage/disengage 4WD to circulate the transfer case.
- 2) Open fill plugs first: Always crack the fill plug before draining. If it’s stuck, you can still drive home.
- 3) Drain: Position pan and remove the drain plug. Expect strong gear‑oil smell. Let it fully drain.
- 4) Inspect magnets: A fine grey paste is normal. Shiny flakes/chips = bearing/gear wear.
- 5) Clean & prep: Degrease plugs/threads, replace flattened washers.
- 6) Refit drain plug: Torque about 35–40 Nm (don’t overtighten—threads strip easily).
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7) Fill: Pump in oil until it just seeps from the fill hole on level ground.
- Gearbox: ~1.5–1.7 L (stop when it weeps).
- Transfer case: ~0.9–1.0 L (stop when it weeps).
- 8) Seal & clean: Refit fill plugs (35–40 Nm). Wipe spills. Road‑test and recheck for leaks.
Russian & Eastern Bloc extra tips
- Cold‑weather shifting (gearbox): At −20 °C and below, idle in neutral with clutch engaged for 2–4 minutes to get oil moving before driving.
- Top cover service (gearbox): If the lever feels sloppy, renew top‑cover bushings while oil is out. It transforms shift feel.
- Noise tuning (transfer case): Many report that synthetic 75W‑90 trims whine on older gear‑driven cases.
- Breather hygiene (both): Clean or extend breathers high into the engine bay to prevent water ingress after mud/rivers.
- 4WD circulation: After filling, engage/disengage 4WD on loose ground to move fresh oil across selector shafts.
- Field spare: Carry 0.5–1.0 L of your chosen oil—handy for top‑ups after hard off‑road days.
Urgent warning signs
- Hard or notchy shifts, especially when cold (gearbox).
- Whine/howl at steady speeds (either unit).
- Fresh leaks at pinion/input/output seals.
- Cloudy/grey oil or obvious metal on the drain‑plug magnet.
Quick Reference (Gearbox & Transfer Case)
| Unit | Spec & Capacity | Action | Why it matters |
|---|---|---|---|
| Gearbox | GL‑4, 75W‑90 (cold) / 80W‑90 (hot); ~1.5–1.7 L | Change 35–40k km (15–20k heavy use) | Protects brass synchros, smooth shifts, less wear |
| Transfer case | GL‑4 or GL‑5; ~0.9–1.0 L | Change 35–40k km (after water crossings: now) | Quieter running, protects gears/bearings & seals |
| Breathers | Clean / extend high | Each service (or after mud/water) | Prevents water ingress & pressure‑pushed leaks |
| Torque | Drain/fill plugs: ~35–40 Nm | On refit | Avoid stripped threads, ensure proper sealing |
UAZparts Pro Tips
🔧 Open the fill plug first. If it’s seized, you haven’t stranded yourself with an empty box.
🌊 After deep crossings, assume contamination. Drain immediately—even if the oil “looks ok” from the fill hole.
🧊 In Siberian temps, synthetic 75W‑90 makes the first km far gentler on bearings and synchros.
🪛 Replace crushed sealing washers and clean the plug magnets every service—cheap insurance.
Need the right GL‑4/GL‑5 oils, pumps and sealing washers for your UAZ?
See our complete Oils & Fluids Guide
See our complete Oils & Fluids Guide
Questions about climate, loads or specific gearboxes/cases? Tell us your model and usage—we’ll recommend a proven combo that Russian owners trust.