ZF 6-speed manual conversions for Discovery 3/4, ZF automatic metal sump conversions, transfer case rebuilds.
Gearbox work is some of the most specialised mechanical service we carry out at Davis Performance Landys. Land Rover gearbox conversions — particularly the Discovery 3 and 4 manual conversion and the ZF automatic metal sump upgrade — require detailed knowledge of the vehicle architecture, transfer case integration, and the correct parts supply to do properly.
Land Rover fitted the Discovery 3 and 4 with a choice of manual or automatic transmissions in most markets. In Australia, the TDV6 was predominantly sold with the ZF 6HP26 automatic. For owners who prefer direct manual control — particularly for off-road driving and towing — a ZF 6-speed manual gearbox conversion is available. This uses the correct gearbox variant designed for the Discovery 3/4 platform, ensuring compatibility with the transfer case, propshafts, and vehicle electronics. The manual conversion fundamentally changes the driving character of the vehicle, giving the driver direct engagement on difficult terrain.
The standard ZF 6HP automatic gearbox has a plastic transmission oil pan. This pan is a known reliability concern — it can crack, deform under heat, and the integrated filter is not readily serviceable without replacement. We supply and fit the ZF metal sump conversion kit, which replaces the plastic pan with a machined aluminium unit. The metal sump also has a larger capacity, improving thermal management of the transmission fluid and extending service intervals. This is a recommended upgrade for any Discovery 3, Discovery 4, or Range Rover Sport with the ZF 6HP gearbox prior to any heavy-duty towing or outback travel.
Many ZF automatic gearbox "faults" are caused by degraded transmission fluid rather than mechanical failure. The ZF 6HP was factory-filled with fluid rated for "lifetime" use — a designation that has been widely discredited in practice. We carry out ZF fluid and filter changes using the correct Esso LT71141 fluid specification, which often resolves shift quality issues and stored gearbox fault codes without any mechanical intervention.
Gearbox work is booked in advance with adequate parts lead time. Contact us at 18/62 Argyle St, South Windsor NSW or call (02) 9679 1978 to discuss your specific requirement.
Yes. The ZF 6-speed manual gearbox was fitted to some Discovery 3 and 4 variants in overseas markets, and the conversion is achievable using these components. It involves replacing the automatic gearbox and its associated components while retaining the original transfer case and propshaft attachment points. This is complex work requiring specialist knowledge of the Discovery 3/4 drivetrain architecture — contact us to discuss feasibility for your specific vehicle.
The ZF 6HP gearbox fitted to Discovery 3, Discovery 4, and Range Rover Sport models has a plastic transmission oil pan. This pan can crack over time, particularly under heat stress. The metal sump conversion replaces it with a precision-machined aluminium pan that also holds more fluid. The increased fluid capacity improves thermal management of the transmission, and the metal pan eliminates the cracking risk. We recommend this as a standard upgrade before towing or outback travel.
Despite being marketed as "lifetime fill," we recommend changing ZF 6HP gearbox fluid at 80,000–100,000 km intervals under normal use, or at 50,000 km intervals on vehicles used for heavy towing or off-road driving. The correct fluid specification is Esso LT71141 (or exact equivalent). Using incorrect fluid or extended change intervals is a leading cause of ZF gearbox shift quality degradation.
Not necessarily. Harsh or delayed shifts on the ZF 6HP are frequently caused by old fluid and a blocked filter rather than mechanical failure. We start with a fluid and filter change using the correct specification. In many cases this resolves the shift quality issue entirely. If there are mechanical issues beyond fluid condition — worn clutch packs, solenoid faults — we diagnose from there.
Defenders used the LT77 5-speed manual (earlier models), R380 5-speed (later), and some exported vehicles had automatic options. Both the LT77 and R380 are fully rebuildable. We carry out gearbox resealing, synchro replacement, and full rebuilds on both units. The R380 is a strong gearbox when properly serviced; the LT77 has a reputation for second-gear synchro wear on high-mileage examples.
Yes, this requires careful integration. On vehicles with Terrain Response (Discovery 3/4, Range Rover Sport), the gearbox communicates with the transfer case and traction control systems. A manual conversion requires that the relevant control units are correctly configured and that any chassis-CAN communications from the original auto gearbox module are handled. This is part of the conversion process we manage — it is not simply a mechanical swap.
Yes. The Discovery 2 used the R380 5-speed manual, same as the later Defender. We carry out oil seal replacement, synchro repair, and full resealing on R380 units. The most common Discovery 2 R380 issue is oil leaks from the main shaft rear seal and the gear lever housing. Contact us if you have specific concerns — many R380 issues are reseal work rather than full rebuilds.
Our South Windsor workshop is ready to help. Contact us today and we'll get back to you promptly.