Help with oil leak!!! Defender 90 2.5 na

Hi guys hope you are well.
Since owning my Land Rover 90 1991 2.5 na ( 2 months lol) Ive had a oil leak coming from the rear main seal area behind the gearbox.
It started off as a few drops every few days but since oil change to drivetec 10w40 the leak has gotten worse.
Here are some points on the leak.
1. Doesn’t leak much when engine not running.
2. Worst when parked on idle engine on
3. Some days worse then others
4. Sometimes it’s a few drops other times it’s a small puddle.
I’ve tried wynns stop leak which helped Alittle or maybe thsts convincing myself lol.
ive been told it could be the rear main seal or cross crucifix seals but no one seems to know much when I go to local mechanics.
I’d like some info before I go to fix it as if it’s the main seal I’ve been quoted engine out £500. They said cross seals are easier and cheaper to do but can’t garantee the works.
I’m in Nottingham
I’ve tried to take a few pics
Appreciate the help in advance guys.

Few more

First thing is that is not the gearbox , it is the the bell housing where the clutch lives between engine and gearbox.
Also I can see someone has fitted a wading plug in the housing drain hole [ only usual to fit when one expects to do some deep water stuff ]
I suspect the previous owner fitted it to hide the fact that the engine crankshaft main seal is leaking. I recon if you pull that plug a lot of oil will come out.
Bad news is clutch will now be badly contaminated and need replacement. However as the seal needs doing and either engine or box has to come out to do this and given the amount of work it is usual to replace clutch anyway.
No idea what cross seals are supposed to be but there are T seals on the engine rear main bearing.
You need to find someone in your area who knows Landy's as the crank oil seal is a job that has to be done correctly.
You may be interested in You tube videos for Land rover 19j. 200tdi crank seal replacement. 300tdi and later are different.

Thanks for your help mate

Sorry to be the bearer of bad news, hope you get it sorted.

tottot said:

Sorry to be the bearer of bad news, hope you get it sorted.

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it’s ok mate I’m just sourcing a local in nottingham now. Do you know how much this sort of job would cost labour wise, I know the seal is about £10 lol

I do nearly all my own repairs so can not help with labour costs. Others may be able to say more. One thing you must do is get a quality OEM seal, the cheap ones do not last.
Also a 1991 would have a TDI 200 from new not a NA engine.

tottot said:

Also a 1991 would have a TDI 200 from new not a NA engine.

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Not necessarily, they were still available with the NA engine from new, quite why anyone would choose it over the 200tdi is a mystery! Maybe for continuity or familiarity?