What's the correct ratio of posi additive to gear oil in the rear end?

[Michael L.]

Guys,

I'm getting ready to attempt to use some thread sealer to stop a slight leak from a rear spring bolt on my '69 that I inserted before I read on the forum that these bolts need to be shortened. I have since shortened the bolts, but I still have a slight leak to address. I am anticipating that when I remove the bolt I will get some gear fluid leaking out that will have to be replaced, plus the small amount that has leaked out already. When I originally filled the rear, I put the posi additive in and then topped it off with the gear fluid, so I didn't have to worry about the correct ratio. When I top it off I want to combine the posi additive to the gear oil in the correct ratio and then use it to top off the rear. Does anyone know what the correct ratio is?

Thanks,
Mike

[Mark E.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

One 4 oz bottle of additive is recommended; total capacity is 4.25 pints or 68 oz. That's a ratio of 4:64 or 1:16.

[Joe L.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

Guys,

I'm getting ready to attempt to use some thread sealer to stop a slight leak from a rear spring bolt on my '69 that I inserted before I read on the forum that these bolts need to be shortened. I have since shortened the bolts, but I still have a slight leak to address. I am anticipating that when I remove the bolt I will get some gear fluid leaking out that will have to be replaced, plus the small amount that has leaked out already. When I originally filled the rear, I put the posi additive in and then topped it off with the gear fluid, so I didn't have to worry about the correct ratio. When I top it off I want to combine the posi additive to the gear oil in the correct ratio and then use it to top off the rear. Does anyone know what the correct ratio is?

Thanks,
Mike

Mike------


I recommend adding TWO 4 oz bottles. That's partly because the formulation of this product that's been available for the last many years is not as "potent" as the original formulation.

[Michael L.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

Thanks guys much appreciated.

Mike

[Gary B.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

I believe that Gary Ramadei also now recommends using 2 bottles of the currently available GM additive.

Gary

[Duke W.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

One 4 oz bottle of additive is recommended; total capacity is 4.25 pints or 68 oz. That's a ratio of 4:64 or 1:16.

My technical data states axle capacity is approx. 3.7 pints, total and this would be for all C2/3 with the cast iron carriers.

All manufacturers who offer clutch type LSDs sell the same friction modifier - GM, Ford, DB, BMW... whatever. You can buy it at NAPA, and it's probably cheaper, NCB4285V, and you can probably cross reference this to whatever your most convenient FLAPS store sells.

Duke

[Gary R.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

Hi Gary,
Yes, for the past 9-10 years or whenever the packaging and number changed so did the "action" if you will. I used to use just 1 bottle per diff and all the diff's I build are tuned, so no spring packs. I never had chatter with a tuned posi until the change as mentioned. 2 bottles resolved it with no side affect.

[Michael L.]

[Lawrence S.]

Re: What's the correct ratio of posi additive to gear oil in the rear end?

Mike------


I recommend adding TWO 4 oz bottles. That's partly because the formulation of this product that's been available for the last many years is not as "potent" as the original formulation.

I agree with Joe, I always use two and seem to have better results.

Sorry to hear about your carrier. I wish the suppliers would sale the correct length bolts. I ended up evap o rusting my originals and reused them in my 67 BB while restoring the rear suspension.

Good Luck!