Gearbox Top Leaks

Anyone with a Series Land Rover will be familiar with leaks from the top of their gearbox, running down the sides and dripping from the drain plug. The sources of these leaks are threefold.

breatherselector cover and stickThe breather in the steel cap on the centre of the selector rod cover tends to let a lot of oil out, and in some cases, that steel insert can be loose within the aluminium cover, also allowing oil passage. I removed the insert and, after degreasing, applied a bead of silicone around its seat. I also blocked off the plastic breather with silicone permanently. The higher breather, on top of the square plate at the rear of the selector housing, was then replaced with a Defender gearbox remote breather. This will not only prevent oil loss through the breather, but also any dirt or water ingress.

The reverse and 3rd/4th selector detents also tend to leak if the rubber grommet around the spring isn’t compressed well by the steel L-plate and gearbox casing. Thankfully, mine are good.

new sealsold sealsThe final source is from the selector shaft seals, underneath the gearstick mounting. I removed the selectors to fit new replacement seals. The newer type are a combination of O-rings and expanding plastic washers, and they are a much tighter fit than the loose square-section seals fitted as standard. The washer just packs out the remaining depth of the original seal groove, and also acts as a dirt scraper to prevent dirt erosion of the O-rings.

Before refitting the gear stick, I fitted a new O-ring to its bottom ball to prevent rattling, and having cleaned out all traces of oil based grease from the selector rod cups, applied a generous amount of graphite grease that will not perish the anti-rattle O-ring like before. I also fitted a new anti-rattle spring to the transfer box lever.

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  1. Andy Withers says:


    We have corresponded on Land Rover UK Forum and you have been of great help regards OD rebuild. Currently awaiting delivery of new main shaft for mine.

    Rather than starting a new thread on the Forum, could you advise where you obtained the anti rattle rubber seal for your gear lever. I’ve tried various methods, but nothing that lasts more than a couple of weeks. Road bike inner tube works well, but not for long. I need to cancel out some of the noise since running without the OD. Fingers in ears time.



  2. Hi Andy,

    At the moment, I’ve just replaced the original worn O-ring with another 3mm thick one from an O-ring kit I bought a while ago. It has done about 250 miles without any apparent wear – the last one gave up and rattles at about 500. I think the big difference was using graphite grease instead of heavy (oil based) grease; the graphite grease doesn’t react with the rubber. Copper grease may also work.

    I might see if I can find a suitable polyurathane O-ring, which should be a bit tougher.

    I’m glad that the overdrive rebuild guide is helping – good luck with that.


  3. Nick Smeets says:

    Hi Nick,

    I came across your blog by searching for a solution to prevent the selector shafts from oil leaking. How does this solution work for you after a few years, and even more important: can you tell me how the expanding plastic washers are called, or where to get them? I have been looking for them here in the Netherlands, but they seem to be obscure parts,

    Thanks in advance!


  4. Hi Nick,

    I found they weep or sweat oil at much the same rate as the standard seals, so I wouldn’t bother changing them. The weeping makes a small mess, with the occasional drip on the driveway, but is not significant to oil levels in the box – the significant source of leaks there is via the interface between the rear bearing carrier and main casing into the transfer box because LR and every reconditioner fail to use a bearing seating compound or sealant in that joint as specified by LR.

    As for the selector seals, the best thing to stop them weeping would be to add a bottle of seal reconditioner fluid tot he gear box oil – this softens and swells the rubber, preventing cracking or perishing and tightening the seal. However, a small amount of oil loss here is not a bad thing – it keeps the selector rods oil coated and rust free.


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