Filling the Ford LSD diff wih lubricant.

[jcaswell]

My diff hold 1.1 litres, according to the specs ,is one litre enough . I am using Motul and the bottle is .  1 litre and expensive. Not that I'm cheap though.I do have a second bottle.Do I really need to open the second bottle to add .1 of a litre.

[revilla]

Put 1 litre in and see if it is full to the level. If not ...

[SM25T]

You have already bought a second bottle ... so you won't save by money by under-filling the diff. I would rather fill to the specified level on my car, not wonder if I should open another bottle.

[brianjhall31]

Are you checking the quantity of lubricant with the diff fitted?  If so the only method of measurement is by removing the plug at the rear face and (if nothing comes out) filling to the point where it does.   I use a Machine Mart pump action:

https://www.machinemart.co.uk/p/clarke-cht843-250ml-oil-can/

Usually takes only 3 or 4 pumps during my annual servicing checks to bring to correct level which means a 1 ltr bottle last a long time.   If you need more than 1/2 ltr for topping up you have a seal problem.

[jcaswell]

Ok I opened the second bottle and added til  it ran out filler hole. Took about a 25% of the second bottle. Fully filled and driving no leaks.Cheers Jamie

[Doctor]

Silly question to start with, but you've arrived to the correct conclusion. 

More powerful cars have the brass vent tapped in on top of the rear cover where you do connect the breather hose that lives under the boot floor. Sierra casing for a 7 inch diff with a big ass LSD takes about 1.2-1.3 litres of oil. Make sure the car is levelled.