BHPian PhantomLord recently shared this with other enthusiasts.

Finally was hit with Gearbox oil leak issue. While returning from road trip on a hill climb clutch started slipping, this I guess is same RPM increase issue reported by some owners. It was not bad only happened in 3rd gear and above at peak torque RPM only if pushed hard. After reaching destination I noticed clutch smell, there was no doubt clutch was cooked. I think I had this slip from day one, after long drives there was some odd smell near bonnet, since it was mild I thought it could be oil from previous leak getting burnt.

This is same issue as what Manuuj reported earlier. In my case initially there was oil leak via breather hose located above gearbox (over filled transfer case). Gearbox was wet with some oil but I ignored it as related to leak from breather hose, since drain hole(Blue Arrow) did not have oil drip. If you want to verify if your Gurkha has same issue, just remove plate marked in green and insert a paper towel.

After loosening the bolts oil started dripping.

Fly wheel fry, puddle formed by oil leak is picked up by flywheel and circulated to clutch pack.

Clutch Cookie, Cooked pressure and friction plate.

You can see that drain channel needs some porting, channel is too thin and edge is raised a bit, small dirt can block it.

Here is example of 124's GearBox, you can see proper drain channel, which is deep and has raised tongue to prevent oil stagnation like you see in Gurkha (Right side is old straight hole design from W115).

Root cause is loose bolt that is not loose :-), actually bolt is longer by 5mm. Proper fix is to use shorter bolt, parts catalog lists it as M6x20, it should be M6x15.

Looks like Permatex flange sealant is used, which is correct for the purpose but gap should be small. Notice the oil channel(white arrow) partially blocked by excessive sealant. Make sure correct bolt length is used or at least washer is used to correct the excess length, avoid using excessive silicon sealant here.

There is sound and heat insulation on gearbox, not sure of its purpose, it is of good quality though, sound damping part inside looked like one used inside door panels on EU cars.

All drain bolts on Gurkha have magnet

Insulation had some damage and collected lot of dirt, so removed it and cleaned the gearbox.

New Clutch plates: Clutch plates were replaced under warranty, the release bearing boot had a cut and had collected oil, so that was replaced as well.

Fly wheel cleaned and clutch assembled.

Cross member on which Gear box is mounted had to be removed, cleaned and painted it as well. GB mount forms a cup(green arrow), it collects dirt and water so drilled a hole for easy cleaning.

Ready for assembly, did some porting so that oil does not stagnate, didn't make channel deep, was not sure if shallow channel was on purpose for off-road use. Anyway next time you see any oil wetting in this area, GB has to be pulled. After assembly shifted TC into neutral and dry ran the GB for 10 min shuffling between gears.

Pictured after more 300KM of testing

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