Gearbox oil leaking?

Let's go through a few possible causes of manual transmission oil leaks that the Mps's and many other models may encounter based on my experiences in the automotive trade.

In most cases manual transmissions are usually pretty tough and trouble free! ( I don't want to hear about your cold shift or how its the cars fault you crunch gears from being a nut sack rushing shifts or even the oem rem is stuffed)

The most popular leaks are from sealing washers either being used to many times, reused and fitted without cleaning all the grit from surfaces, being over tight because the drain plug holds the rear half of the car on or simple not being tight at all because you are @SarcasticOne LOL!

Sure poor repair practices from relevant work, age and even poor factory assembly can lead to future leaks but there is one cause that seems to set the scene for transmission,transfer case and diff oil leaks.... Over filling!

Gearboxs rely on oil being flung around everywhere just from the rotation of internal parts, the oil experiences some extreme pressures and heat. As the temp builds up in the gearbox so does the pressure inside the gearbox, for this reason there is a small breather/poppet style device that allowes this pressure to escape. Over filling your gearbox will cause the venting fumes to eventually block up this small valve which then means the pressure will build up and be trapped until it finds away to escape ie; seals, weak sealed surfaces.Ever undone a fill plug to check level and been spat at?

These poppet valves have been blocking for years on 4wd gearbox and usually the 1st thing to be removed and replaced on diffs of serious 4wd owners who do water crossings.

What does this translate to for the Mps you ask?! The shift shaft seal has been know to appear to leak, oil leaks don't usually come from top points of transmissions that don't run pressurized oil lubrication systems.

The shift selector assembly can be removed relatively easy for repair or modification to rid of that painful little oil leak:)

Minor things to think about before attempting this repair are as follows,

: the shift cables need to be unclipped- break one of these and the repair bill will sky rocket!
: the gearbox mount may need to be removed- support the gearbox!
: depending on how you tackle the repair you may require tools that aren't usually in home kits- get correct tools (hitting things is dodgy)

The job time for myself was 2hrs, I would expect most workshops to charge around 3hrs if they did replace the items I did.

Before getting carried away with attempting this whole job I would strongly suggest replacing the poppet valve, removing it and cleaning it won't be an option due to its construction and should be available from a local transmission shop, however if you are going to go balls deep the poppet valve can remain in the housing and cleaned once disassembled during seal replacement.
Alternatively it could also be replaced with a hose barb and breather line (like what 4wd owners do to the diff breathers)


still adding more...