The oil in the diff in my car is about 10-12 mm below the filler hole so a bit low. I drained the oil in this diff and refilled it around 1976-77. Don't remember what brand of oil I refilled it with other than it would have been the correct type at that time for this diff.(seem to think it may have been a Castrol oil and I am fairly sure that it was a luminous blue colour?) Took the car off the road late 1978 and restored it from 2012 -2016. Fitted new wheel bearings at this time and probably lost a bit of oil while doing this. The car has travelled close to 99,000 miles with about 2,500 of those miles since registering it in December 2016.

I have some questions about topping up the oil in the diff, or changing it:

1. What type of oil do buy these days to use in this diff? I have been advised to to use the following oil - Brad Penn - Grade 1 Limited slip. - GL - 5 SAE 80W. - 90 gear oil. Yes/No?

2. Is it better to drain the diff and refill it with the current correct type of oil than to add this oil, to the existing oil in the diff? Yes/No?

3. If I drain the oil in the diff should I flush the diff while the cover is off? I ask about flushing the diff as I did this once on another ten bolt lsd (taken from a car that I didn't get to drive - so no idea of what it sounded like) When I put this diff into another car I had then it had a whine whenever you backed off. I was told the whine was a result of flushing the diff?

Any comments appreciated

Gerard

Manual says Gm lubricant 9985035 only, and I remember an old bloke I knew telling me never put a normal LSD oil in it, only the specified stuff due to the cones v clutch pack on other lsds . I don't know if that's right or wrong, but I would look into it if I were you