Tank 300 PHEV Off-Road Maintenance — Service Guide for Heavy Use

The Tank 300 PHEV (Hi4-T variant) is GWM's serious off-roader — body-on-frame construction, three locking differentials, transfer case, full-time 4WD with low-range. Combined with a 1.5T Atkinson plus ~37 kWh battery for hybrid power. Off-road use changes the maintenance schedule significantly from on-road-only spec.

Standard Tank 300 PHEV service interval

• First inspection: 5,000 km / 3 months
• Routine: every 10,000 km / 12 months
• Major: every 40,000 km / 4 years

Off-road use — halve every interval

If you actually take this off-road (not just look the part), the standard schedule isn't enough. After any of the following, do a post-trail inspection:

• Water crossing (wading)
• Mud, sand, or deep snow drive
• Rock crawl / scraping the underbody
• More than 4 hours of low-range work
• Driving on heavily corrugated washboard for 1+ hour

Post-trail inspection (do EVERY time)

1. Underbody hose-down — wash off mud and salt with low-pressure water (high-pressure can force water past seals).
2. All differential breathers — check they're not blocked. Blocked breather + cold water crossing = water sucked into diff via vacuum.
3. All three diffs (front, rear, transfer case) — check fluid for milky colour (water contamination). If milky, drain and refill same day.
4. Wheel bearings — listen for grinding on first 10 km. Water crossings kill wheel bearings.
5. Brake calipers and slide pins — mud packing reduces braking. Wash and re-grease pins.
6. Suspension bushings — check for tears (rocks or branches).
7. HV battery underside — visual check for impact damage. Tank's battery is well-armoured but extreme rock work can dent it.
8. Skid plates — retorque if loosened.
9. Tyre sidewalls — check for cuts.
10. Cabin filter — dust and pollen accumulate fast.

Halved-interval schedule for regular off-road use

| Item | Standard | Off-road |

|------|----------|----------|

| Engine oil | 10,000 km / 12 mo | 5,000 km / 6 mo |

| Transfer case oil | 60,000 km | 30,000 km |

| Front diff oil | 60,000 km | 30,000 km |

| Rear diff oil | 60,000 km | 30,000 km |

| Cabin filter | 12 mo | 6 mo |

| Brake fluid | 24 mo | 12 mo |

| 12V battery check | 12 mo | 6 mo |

Transfer case and diff fluid specifics

The Tank 300 has three separate housings, each with its own fluid:

• Front diff: GWM-specified gear oil 75W-90, ~1.0 L
• Rear diff: GWM-specified gear oil 75W-90, ~1.2 L
• Transfer case: GWM-specified ATF (different from petrol-only Tank 300 — PHEV variant uses a specific spec)

Consult dealer for current OE PNs. Don't substitute generic gear oil — GWM bulletins call out specific friction modifier needs for the limited-slip behaviour.

Hybrid system after off-road use

• HV battery: if you've gone deep into water (over wheel hubs), get a workshop HV insulation test.
• DHT transmission: sealed, but heavy load cycles in low-range stress the wet clutch packs. If you wheel hard often, change DHT fluid at 30,000 km.
• Battery cooling pump: mud can clog the radiator/heat exchanger underneath. Visual check after dirt drives.

Year-by-year cost (off-road regular use, EU averages, 2026)

| Year | Mileage | Service | Cost |

|------|---------|---------|------|

| 1 | 10,000 km | Severe routine | €180-260 |

| 2 | 20,000 km | Routine + brake fluid | €280-400 |

| 3 | 30,000 km | Routine + diff oils + transfer case | €550-800 |

| 4 | 40,000 km | Major: oil + brake fluid + 12V + A/C + DHT inspection | €650-950 |

| 5 | 50,000 km | Routine | €180-260 |

5-year off-road total: ~€1,840-2,670. Pure-road equivalent: ~€1,250-1,800.

Common off-road mistakes

1. Skipping post-trail underbody wash (salt and mud accelerate corrosion).
2. Using high-pressure spray (forces water past seals).
3. Generic gear oil in diffs (wrong friction modifier).
4. Ignoring milky fluid in a diff (water contamination kills the gears in weeks).
5. Skipping breather check (blocked breather + cold water = vacuum-suck water in).
6. Not retorquing skid plates after rock work.

Where to source Tank parts

Browse Tank 300 PHEV spare parts at EV Crate. For other Tank models see Tank 400 Hi4-T, Tank 500 Hi4-T, Tank 700 Hi4-T, and our full Tank catalog.

FAQ

How often should the Tank 300 PHEV be serviced?

Standard: 10,000 km / 12 months. Off-road regular: halve everything to 5,000 km / 6 months for engine oil and most fluids.

Do I need to change all three diff oils?

Yes, every 60,000 km on-road or every 30,000 km off-road. Each housing has its own fluid.

Can I use generic gear oil in the diffs?

No — GWM specifies friction modifiers for the limited-slip behaviour. Generic 75W-90 will degrade lock performance.

What happens if my diff fluid looks milky?

Water contamination from a crossing. Drain and refill same day. Otherwise the gears rust within weeks.

Does the HV battery need waterproofing inspection after wading?

If you've been deeper than wheel hubs, yes — HV insulation test at workshop.

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