Originally Posted by GrantB

Owners Manual says.
SAE Synthetic 75W-140
API GL-5

ATF is a bit thin if you ask me. I think the need is for an oil that can withstand high pressure between mating faces.

Re above, 75w - 140 is quite a high pressure oil, but wondering why it's thin ???

I understand the diffs on these XCF's are a limited slip diff.... if so, do they need a thinner oil to operate ?

most vehicles have a diff oil of EP 75 > 90...., so this one rated at 140 at high temp is good, but im wondering why it is so watery ???

I've used alternative oils to manufactureres recomended before and come a cropper & destroyed axles and gearboxes thinking I knew better .....

But I'm wondering at the logic of this ATF fluid in a rear axle . . . . unless it needs a thin oils for the diff lock to work ???

saying that, My landrover descovery uses a special ATF fluid in its main transmission manual box.....
But anything else simply was too thick and you couldnt change gear and the synchro simply would not allow u to change gear let alone put it in gear, and other oils would destroy a box in 5,000 miles totally.

Penny for your thoughts ??

Regards to all.
Grant B