CHANGING THE HIGH RATIO GEARING

MOST DEFENDERS seem low geared for motorway and main road driving. It’s practical to increase the gearing by around 15 per cent by swapping the gears in the transfer box for a higher ratio Discovery gear set. This only increases high ratio, leaving low ratio as standard, which might be needed for off-road or towing work. But, with Tdi Defenders and especially the earlier (pre-tdi) Ninety and One Ten models, the engine has to be in good fettle to pull the increased high ratio, and it’s important also to consider the type of use the vehicle will be put to, and whether the vehicle has already been effectively up-geared by fitting oversize tyres.

The differences between Discovery and Defender gearing are not straight-cut. For example, the early Discovery Mpi model has a lower high ratio, similar to that of the Defender’s 1.41:1 ratio. Conversely, the 50th Anniversary Defender 90 (if you’re lucky enough to own one) and the TDCI models have a 1.211:1 ratio, similar to a late Discovery 1 and all Discovery 2 models. There are other anomalies, such as the 2.5-litre naturally aspirated One Ten which has a very low 1.667:1 ratio, in which a Discovery ratio would be too high for heavy towing, given the low engine performance, though an increase to the Defender 1.41:1 ratio might be practical.

Higher gearing is unlikely to provide any meaningful reduction in fuel consumption, so don’t expect a return on the investment, though it will noticeably cut noise levels at speed.

A Discovery transfer box can be fitted A ratio change needs the transfer box out of the vehicle and a full strip down. Options: increased high ratio (left), standard ratio (centre), and extra low (right) which can counter the effect of larger tyres. into a Defender (no point in TDCI which has the same ratio as Discovery), but two M8 holes will need to be drilled and tapped into the casing to accept the Defender handbrake linkage in place of the Discovery’s cable-operated system. If using a Discovery 2 transfer box the diff lock linkage may need to be swapped over if not already fitted.

Discovery gear sets are available from suppliers such as Ashcroft Transmissions. To install a gear set, the transfer box needs to be removed from the vehicle, and it’s wise to consider replacing bearings and seals while the unit is dismantled, for which rebuild kits are available.