Here is some question I got from an earlier thread from User: portland bill
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Oil leak is possibly the easiest, look for the highest point of the leak. If you can't find it, clean everything and look at it regularly until the source is apparent.
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The leak apears to be coming from the top of gearbox and covers the whole of the top. I can only assume it comes from the selector cover that I had to remove because I could not change gears. Removed the gear selector rod from the wrong place and selector stopped working hence the cover needed to come off. There does not seem to be a gasket between the selector cover and gearbox so I put it back on the same way as when I took it off. May I should have put some gasket sealent? There is no mention of selector removal/fitting in the Heynes manual so don't know for sure how this is done.

The top of the gearbox became wet during the clutch change because I had to replace the clutch slave cylinder, which meant I had to drop quite a bit of brake fluid on the gearbox, but I suspect the brake build would have evaporated by now as the gearbox still looks wet at the top.

As the leak is not that significant I shall monitor things to confirm the source of leak before I make a move to try to fix this.

Brake fluid doesn't evaporate.

Sniff and Feel.

Transmission fluid smells very pungent, rather like cat pee.

Brake fluid feels soapy between your fingers.

Engine oil is neither.

Probably just resudual brake fluid. Was the failed clutch slave cylinder the cause of the inability to change gear?

Cheers guys, for the responses.
I'll need to wait and see if the leak continues to judge for sure. I hope is brake fluid but I have to be caucious. The fluid looks light like brake fluid but the gearbox oil I chnaged recently looked just like that. There is no obvious smell so I might be OK.
The slave cylinder was not the cause of the clutch failure, it just desintegrated when I removed it so I can drop the gearbox. The rubber boot on the slave cylinder push pin was split so it needed a new one which means I got a new slave cylinder anyway. The clutch plate was on the last legs and one of the three anti vibration springs came off the clutch plate causing the clutch plate to be permanently engaged which means I could not change gears.