1970 differential best fluid

[70-360fe]

1970 f-100 ranger xlt, what would be the best differential fluid to put in? Thanks.

[TNIceWolf]

I expect that you are going to get quite a few different opinions on this. For my own needs I go with an 80/90 weight gear oil in my old F350 with the Dana 70 differential. I have seen other members here advocate 50 weight and a good many synthetic blends as well. It seems to boil down to what you use the truck for and a matter of personal preference most of the time.

[70-360fe]

I expect that you are going to get quite a few different opinions on this. For my own needs I go with an 80/90 weight gear oil in my old F350 with the Dana 70 differential. I have seen other members here advocate 50 weight and a good many synthetic blends as well. It seems to boil down to what you use the truck for and a matter of personal preference most of the time.

Driven daily do some light towing, read about royal purple but 21.00 for one contianer. Was thinking either lucas, mobil ls or a sythenic. Oh how much fluid do I need to fill the differential.

[TNIceWolf]

That will depend on whether you are just topping off the fluid level or filling a " dry " unit after repairs. To fill it or check the level remove the level inspection plug and stick a finger in the hole to feel for oil. If you feel it no problem....just replace the plug. If it is low I wouldnt buy more than a Pint at a time and check again. It is indeed some expensive lube. My diff is probably much larger than yours and I knew it would probably be pretty low when I had it serviced about a month ago. I knew I had lost a lot due to some leaks and bad seals and then pulling the axles. It was a surprise to find that it only required 2.5 Pints to top that huge axle housing off.

[1970 Hi-Boy]

Driven daily do some light towing, read about royal purple but 21.00 for one contianer. Was thinking either lucas, mobil ls or a sythenic. Oh how much fluid do I need to fill the differential.

I would go with Mobil 1 from your list of choices. It should take approximately 6 1/2 pints.

[Donnie]

This is really a LOADED question There are so many good fluids on the market today that one will go crazy trying to decode the misfits from the good stuff..... I use Shell Rotella in all my diesels & Castrol products in most everything else........No facts to back up my opinion, other than the long service life that my units have endured..........there are many trick fluids on the market now that many are confused...
Probably some better & i'm sure some worse than what I use...I have no background in fluid tech, so I am not qualified to opine...Donnie

[hedz]

i got some amsoil stuff in there. probably a waste of money. use a zddp additive or phospherous pills or something the new stuff is made of stupidity

[71PA_Highboy]

zddp is only important in engines, not gears...

[hedz]

zddp is only important in engines, not gears...

zddp aka zinc and phospherous compound or a zinc or phospherous supplement has a huge impact on metal to metal interface especially your rear diff plenty of publicly available evidence to support this(online publications, hardback publications, recorded studies, patents etc etc.). i've worked with some old farts who would drain the rear diff out of ol school rods and taste it for burn quality and use it in their rods for this very reason - the old formulas were far superior and to make a new formula measure up there is almost always supplementation through additives involved.

could have saved a rear end on my fathers nissan titan with a additive. the mistake costed him a pretty penny. if you are not aware of these issues i highly suggest spending a few hours researching. atleast older rear end setups have a higher likely hood of being exposed to these formulas at one time or another - the adhesion/bonding and protection resulting from their uses can last longer than you would think

[Wilma-Colorado]

As a forum newbie with no pedigree, let me say I agree with Hedz. The zinc and phosphorus in gear oil is very important. My experience is with (mostly Japanese) motorcycle engines where the engine oil also serves as a lube and coolant for the primary drive, clutch, and transmission. When you are in the auto parts store and see one or another brand of oil labeled "Motorcycle Oil", it's not just a marketing gimmick. Turn the bottle around and look at the rating. Usually you will see SG, and never beyond SJ. The reason is that the EPA/DOT/Fed Gov has required (much) lower quantities of zinc and phosphorus in more recent oils. Something to do with the environment, I'm sure. If you run modern automotive oil in your single-lube motorcycle engine it will cut it's life dramatically. The wiping action of helical or hypoid-cut gears transmitting multiplied torque and high horsepower at high rpm destroys the oil's ability to both cling and stay slippery, that's what the absent zinc and phosphorus would have done if they were in there. Same for truck transmissions and axles Just my 2 cents worth with a sprinkling of related experience.

Wilma

[colnago]

If you run modern automotive oil in your single-lube motorcycle engine it will cut it's life dramatically.

As I recall, that's because the oil in the motorcycle isn't just for the engine, but also for the tranny/clutch. Regular auto oil in a motorcycle is too slippery for the clutch plates to grab. That's what I remember, by the way; please correct me if I'm wrong. I have no idea if it's because of the metals/additives in the oil or not.

Joseph