OK from Castrol I got a reply which makes sense:
Hi Dave,
Early EP additives were active sulphur – and when it got hot this could be quite aggressive to yellow metals so it was always suggested not to use hypoid oils in units with yellow metals. Hypoid oils are normally found in back axles where the gears have greater loads and these normally have a GL-5 rating. Modern additives tend to be less aggressive, but we normally suggest as a safety margin to not use GL-5 rated products in synchromesh units and ones with yellow metals.
GL-4 EP ratings are classed as “mild” and are what I would suggest would be suitable – we also have some “Universal” products that can cover GL-5/5 ratings using specialised chemistries that again, are not aggressive as the old additives.
I would suggest Castrol EP 80W-90 would be suitable, or better still – Universal 75W-90 which is a part synthetic and a good all round oil suitable for low and high EP requirements. Being a 75W-90 means low viscosity when cold for easy gear change and the working viscosity is a 90 meaning good lubrication and wear protection.
So that is what Castrol recommends for the LC 80, I will also point out I was specific that it was the H151F gearbox fitted in the 80 that the enquiry was related to. I have also got a reply from Morrison:
Good morning Dave
You will require some additives to ensure protection in your gearbox (GL4) to deal with the moderate conditions of speed and load. This is dictated by Toyota themselves.
Lodexol FS 75W-90 is a total driveline product covering API GL 1- 5. It will contain EP additives but they do not become activated unless they are subjected to the harsh conditions applicable to GL5 conditions (i.e. – if they are needed).
So the Lodexol is a universal oil that adapts to conditions as and when they change.
So that has now thrown the cat amongst the VMX pigeons, and the Morrison reply also appears that is should not cause problems.
As an asides I popped into the local spares shop today and asked him to show me his range of gearbox oils, he brought out a mineral, a semi synthetic and a fully synthetic and ALL were GL 5! I asked to see what he had rated at GL 4, he came out with some no name 80/90w GL4, bottle covered in dust, I looked at the state of the bottle and he answered my question before I asked it, "we don't use this any more so this is the last one, 8 euros for 2 litres".
I think I will see what the specs are that Frank has on his Toyota oil, I will not shoot for it yet as I do not have a lot of faith in the main stealer. Last year I got called out to a noisy Toyota that had the D4-D engine, this has labels all over the engine stating ONLY 15/40W engine oil, Toyota had just serviced it and put in 10/40W. I queried it with the service manager as my Spanglish is better than my clients, he replied it was a cost cutting exercise by Toyota, they now only keep a bulk stock of 5/30 for ALL petrol engines and 10/40 for ALL diesels! He lost a customer with his "I think it should be all right", we purchased another OE filter and stopped at the local BP garage and grabbed some 15/40, change both and the engine was running nice an quiet again, oops sorry off rambling again, ok back on topic, any thoughts on the replies from the above vendors?
It does seem we have no choice to use an oil with an EP content whether we like it and our synchromesh lives will be shortened by that decision, is this what kills off the gearboxes in our Land Cruisers? Thinking of others doing rebuilds in the future are there alternative material synchro's that could be used?
regards
Dave