Fitting an LT230 High Capacity Sump


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Defender_Hi_Cap_Sump : credit: © Trevor Cuthbert
This simple upgrade can help protect a hard-worked transfer gearbox, Trevor Cuthbert reports

Models: Defender, Discovery, Range Rover
Time: 1.5 hours
Cost: £83
Difficulty: 3/5 stars
Parts and costs: From Ashcroft Transmissions: High Capacity sump for LT230, £78; RTV silicon sealant, £5
Work safely: • Wear protective gloves or barrier cream to protect the skin from oils and sharp edges of components.
Ensure the chassis and components are stable and secured before working underneath the vehicle.
Consider wearing a bump cap and safety glasses when working under a vehicle.
Contact: Ashcroft Transmissions Ltd; Tel: 01582 496040; 


My Discovery 2 serves numerous purposes, from being an everyday family car to being employed for business use, which can involve heavy towing. It often tows close to the maximum rated weight of 3.5 tonnes, such as when hauling my low-loader vehicle transporter with a Discovery or 110 aboard. With this fairly heavy use in mind, I am always on the lookout for
any means to reduce strain on the Discovery’s drivetrain.

Ashcroft Transmissions are now offering a high-capacity sump for the LT230 transfer gearbox. It is suitable for most models which possess the LT230 transfer gearbox, but cannot be used with the V8 or TDCi Defender as it will foul the exhaust. The sump increases the transmission oil capacity by over half a litre and incorporates fins as part of the aluminium construction, which will provide improved oil cooling. This will not only provide better protection for the gearing in the LT230, but there should also be a reduction in radiated heat into the cabin. The sump retains the same ground clearance, and it has a boss which can be drilled and tapped to accept a temperature sensor.

Fitting the high-capacity sump is easy, mainly involving swapping the standard cover for the high-capacity sump – although on some Land Rovers (including the Discovery 2 shown here) the gearbox crossmember has to be removed first. The sump was fitted while the transmission brake was removed for last month’s brake overhaul feature, giving better access for pictures, but the job is equally simple with the transmission brake in position.

Removing the old sump

Step 1: The LT230 transfer box takes 2.3 litres of oil from dry, or around 2 litres when changing the oil. It needs to be drained of oil for this job.

Step 2: The bottom cover of the transfer box is held by a series of ten bolts and locating studs. Note the black RTV silicon sealant gasket.

Step 3: The cover is removed by undoing each of the M8 bolts using a 10 mm socket wrench or a spanner, retaining the bolts for fitting the new sump.

Step 4: The nuts on the (usually two) studs  are removed with a 13 mm spanner. Support the cover as the nuts are removed, to prevent it falling.

Step 5: On this freshly rebuilt transfer gearbox, the cover is still held firmly in place by the sealant, even after the fixings have been removed.

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Step 6: With the cover off, and looking up from directly below the transfer gearbox, the visible gears are in pristine condition, as the box is new.

Fitting the upgrade

Step 7: All of the remaining RTV silicon sealant needs to be scraped away from the cover mounting face, taking care not to cause scoring or gouge damage.

Step 8: The new high capacity oil sump has a range of fins along the bottom to increase surface area, resulting in improved cooling of the gearbox oil.

Step 9: Fresh RTV silicon sealant is applied to the mounting surface of the new sump, taking care not to apply too much to avoid excess in the gearbox.

Step 10: The new sump is placed over the locating studs and the bolts re-fitted. The clear RTV is squashed outwards and the excess can be wiped off.

Step 11: The bolts are tightened progressively, working from the middle out to the edges, creating an oil-tight seal between the sump and the transfer gearbox.

Step 12: On this Discovery 2, the gearbox crossmember is offered up and held by the transmission jack, before being bolted in position.

Step 13: It is crucial to remember to refill the transfer gearbox with EP90 gear oil. It is filled until the oil is level with the filler hole.

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