The right differential addtive for the C2

[Ralph Murdaugh]

Hi guys,Can anyone please tell me what's the best,differential oil & posi.addtive to use in my C2 small block. Thank you. YG

[Wayne P.]

Re: The right differential addtive for the C2

Your GM dealer has the posi-additive.

[Gary S.]

Re: The right differential addtive for the C2

This is the only way to go, even if you use a differential lube formulation that claims to have the additive in it.

Gary

[Duke W.]

Re: The right differential addtive for the C2

You can use any SAE 80W-90 GL-5 gear oil, which is commonly available at auto parts stores. This is also the correct oil for vintage manual transmissions.

For Positraction axles add one 4-0z. bottle of 1052358 additive and buy a second bottle for standby. Short fill the axle by a few ounces and allow 100-200 miles for the additive to penetrate the clutch pack. If you get any chatter after this, add two more ounces of additive and top off the oil. If not, just top off the oil. The "full level" is to the bottom of the plug hole when the oil is hot.

The total axle capacity is 3.7 pints.

Duke

[Clem Z.]

make large figure "8"s in a parking lot to get the

lube between the plates. i prefer amsoil syn gear lube because as i posted before GM recommends you change every 7500 miles and the amsoil will run forever

[Duke W.]

Re: make large figure "8"s in a parking lot to get

Where have you seen the "every 7500 mile" change requirment?

There is no change requirement in the '63 Corvette Shop Manual maintenance recommendations, but for my Cosworth Vega, GM recommended changing the axle oil (for Positraction axles) ONCE at 7500, but not thereafter.

From my own experince with Positraction axles, I recommend axle oil changes every 30-60K miles for normal street driving. For track work I recommend changing it about every 1000-2000 track miles.

The Positraction additive does degrade with temperature, but the modern synthetic additive lasts longer than the pre-1970 type that had a small quantity of whale oil like the old "type A suffix A" ATF from the sixties.

Duke

[Clem Z.]

in my 1988 C2500 owners manual

the posi started grabbing at about 7000 miles so i put in amsoil and posi additive

[John H.]

Re: in my 1988 C2500 owners manual

The owner's manuals and Chassis Service Manuals of the era say the diff lube is good for the "life of the car"; however, they never dreamed that would be 30-50 years