Transmission oils

[Daren]

Hi all,
I have a question about oils for the transmission on my gpw, I am now aware that you should not use modern EP90 gear oil in the main gear box and that a mineral sae90 should be used, is this the same for the transfer case and axles, as far as I know the is no brass in the latter. I'm asking as I have loads of EP 90 from my Land Rover ownership and the SAE90 is alot more expensive so if I can get away with only using it the gearbox that would be great.
Regards

[artificer]

Some GL5 oils don't use buffered sulphur EP additives, therefore they can react with yellow metals and corrode them.

Any GL4 oil will be OK, they only have 2/3 the additive levels of a GL5.

Basically if an oil says it's a transaxle oil it should be OK as it's designed for gearbox and diff use, eg. Castrol Multitrax or Castrol Syntrax.

Anything that is dual rated GL4/5 should use buffered sulphur and be safe.

Any diff oil that advertises that it uses a borate rather than sulphur based EP additive should be OK.

Ultimately, if you can find a copper corrosion number on a TDS/PDS, 1a or 1b are absolutely safe.

I'd try a 75W-90 as it should shift better in cold weather.

[dinof]

For 18+ years I used a GL-5 oil in my transmission with no visible signs that the sulfur did anything to the synchros. But I now use Royal Purple synthetic 75W-140W oil as it does say it is safe for soft metals.

[Daren]

Thanks guys.