Just for additional clarification, my understanding is that it's important
the oil be non-detergent for overdrive transmissions. I don't know why,
and I don't know if it's true - I just know that's what experienced people
and manuals say.
> Just for clarification, the gearbox and the OD *share* the same oil.
> Filling, level checking and topping-up is done at the gearbox, but
> you put in the gearbox circulates round the OD as well. As Hans says the
> recommended gearbox/OD oil is the same as for your engine, which depends
> local climatic conditions.
> ----- Original Message -----
>> Overdrive oil should be the very same as engine oil as your gearbox oil.