I was wondering if anyone uses synthetic lube in their differentials. I've been thinking of switching to it and would appreciate any advice. What kind you use and how much will I need. Thanks

 

Dodge specs call for synthetic lube in the differential and that's how it comes from the factory. Are you saying you've put conventional in there???

 

Correct. The rear diff fluid and trans is synthetic. Only the engine oil is dyno oil from the manufacture.

 

No I haven't done anything to it. Thanks for letting me know. I didn't know it was already synthetic. Thanks guys

 

That doesn't mean it lasts for 100kmi. You need to change your rear diff fluid if you never have. It should be done every 15kmi if you tow and 30kmi if you don't. I'd say it's safe to run 40kmi Highway, but ANY city driving mixed drops that down significantly. Ford claims 100kmi for their trucks and there is just no way unless they have miracle oil?
I changed my rear diff at 1kmi for break-in and again at 9kmi. It would have been at 10kmi but I hardley drive it and I got eager..haha I bet 0.001% of car owners do this, but if you were to have new gears installed, you would do the same thing no? Truck tows 60% of the time but at 1kmi when I changed the rear diff which had zero towing miles, had very dirty oil. dark and shiny.

2qts 75w-140
2qts and a bottle of additive should do the trick. If you were to drain the axle tubes and wipe everything dry then 2.5qts plus the tube of modifier. I doubt that'll happen.

 

I change the rear diff at 15k, but I have conventional (Lucas) in it as Auburn Gear claims their LSD won't work properly with synthetic (too slick) even with a modifier.

Front gets changed every 30k as it has synthetic in it...