Gearbox & Diff oil change

[geordie40]

Morning all

Just wondering whats peoples views on gearbox & diff oil change. My car was iva'd 12 yrs ago but build was started about 18 yrs ago (not by me!!), it has a MT75 box and usual sierra diff.

They aren't giving me any issues but looking around web some people say they change every 5-10 yrs some say never and others everywhere in between.

As you can tell im a little bored so looking at things on the car i haven't touched since owning it.

[maca]

Haynes Manual states:-

There is no requirement for periodic oil changing, and no drain plug is provided.

If topping-up is necessary, use clean gear oil of the specified type. Do not overfill.

Frequent need for topping-up can only be due to leaks, which should be rectified

[alanrichey]

I agree.   But make sure you top up with the proper MT75 oil, which is specially designed to last for the life of the gearbox.   Ordinary gear oil is not sufficient.

[geordie40]

If I was going to do it I was looking at this stuff

https://www.opieoils.co.uk/p-147606-granville-mt-75-manual-transmission-fluid.aspx 

 

[agent_zed]

I might be talking nonsense but i recall something about using different oil for gearbox and diff. I think hypoid is ok in diff but not in gearbox as it eats the copper on the syncros or something like that.

hopefully someone will be able to clarify if i have the right end of the stick and if not at least its more of a reason to check the manual for the actual specs just in case 

I hate the smell of diff oil! 

[geordie40]

Never changed diff oil and the sierra doesnt have a drain plug so I think you have to suck it out (syringe!!) or take the back plate off, It was more the gearbox I was thinking of doing as it has a drain plug & a filler plug

[brumster]

12 minutes ago, agent_zed said:

I might be talking nonsense but i recall something about using different oil for gearbox and diff. I think hypoid is ok in diff but not in gearbox as it eats the copper on the syncros or something like that.

hopefully someone will be able to clarify if i have the right end of the stick and if not at least its more of a reason to check the manual for the actual specs just in case 

I hate the smell of diff oil! 

Yes, I have a very specific gearbox oil and it's different to diff *but* that's for a type 9, not an MT75. MT75 might be the same but I can't speak from experience...