Reading up this morning - the Lucas stuff has a decent rep for stopping leaks in transmissions & gearboxes - just use a small amount and add more if needed (seems folks get issues as there is no set amount to use and they overdo it). Seems it has solvents that cause the rubber seals to soften and swell.
There's other similar products that seem to work on same basis.
Alternatively a lot seem to endorse instead using a grease gun to add a very soft grease, which will sometimes block the leak &/or replace the 95W-140 for all intents and purposes.
Welcome feedback, is a shame it's hard to gauge the fluid level in the gearbox, you can really only look at what leaks (I keep a small container underneath and it's very little or top back up until it overflows.
PS. One of the products that seems to come up a lot with leaking gearboxes is JD Corn Head grease.....apparently it's a 0 grade grease but it's thick when stable but thins when aggitated. For this reason it seems to work well in gearboxes with leaks as when its not in use it won't come out and when the gearbox runs it lubricates it very well.
