The gearbox fitted to the L series is the Honda derived PG1 gearbox – so you can blame Honda for the rubbish gearshift and reliability problems! Seriously though the PG1 gearbox was originally used in 1984 in the maestro and montego so it is a little long in the tooth.
The biggest killer of gearboxes aside from sheer abuse, is low oil level. The gearbox oil often is neglected and the leaks are usually very small so hard to spot. As the gearbox only contains around 2 litres of oil it doesn’t take much to leak out to start to cause you problems. The first thing to die in the PG1 box is usually the differential bearings and these are quite a common failure on the high powered cars fitted with these boxes (2 litre turbo petrols). So please folks check the oil level and keep an eye on the differential seals for oil leaks. It could save you a lot of hassle!
Speaking of oil the recommended stuff for the L series is MTF94 which is available from Xparts/Honda/landrover dealers as well as just been released by a major aftermarket manufacturer so some motorfactors will stock it on the shelf. Beware most oil booklets in motorfactors have the wrong oil listed. To be honest though it is the lack of oil that usually kills the box, not the type of oil. Rover have recommended lots of oils for this gearbox over the years, from 10w40 engine oil (changed regularly) to SAE90 to 75w80 oils. The last recommendation was MTF94 so if you can get it use this.
There are 4 oil seals on the gearbox, one for each driveshaft which are the usual weakpoints and these can be replaced in-situ fairly easily. There is also another seal for the gearselector and another for the input shaft from the clutch. Both of these rarely give problems.
There are two specifications of gearbox fitted to the L series. The non intercooled models get the lower “normal” spec gearbox. The intercooled models get the “U” (uprated) spec box. The U spec box has an extra bearing and a thicker shaft inside the gearbox. There isn’t a lot in it in terms or reliability but if you have the choice go for the U spec box.
There are at least 2 different sets of gear ratios available for the L series. The 600 has lower ratios than the 200/400 models as it has larger wheels to make up for it. I’m not sure on the 25/45 etc but I think the ratios are all the same. The part number on the gearbox will reveal all though.
I’ll try and put up a list of the ratios that are available when I get time. I’ve also got a spreadsheet that displays the various ratios and could be very useful if you were brave enough to build a custom set of ratios from the many ratios that are available.