C2 Transmission and Differential Case Drain Plugs

[Gary R.]

I tap the differentials for every customer that wants them, both NCRS or non NCRS members. There is a point where practicality should take precedence. My mostly original 72 has a tapped diff, my 69 has both a tapped diff and Muncie. However, I don't judge my cars so it doesn't matter to me. Interestingly enough, many NCRS guys opted for tapped diff drain plugs.

Whale oil I believe was outlawed by 1972? Joe can confirm, but I believe there has been several revisions of the GM additive over the years. Part numbers and packaging for sure, chemistry I can't say but can say I have seen a difference in performance about 10-12 years ago. With a tuned posi, one bottle was all that was ever needed. After one of the packaging and number changes in that time frame, I did have a posi that chattered. I still had some of the previous additive and replaced the diff oil and used this additive and it resolved the issue. Since then I have been advising using 2 bottles of the additive, in this case the GM stuff since that is what I use. I haven't had any issues since. Again, I build posi's in the non traditional way, no spring pack at all. Axle end play 005-007"

Also the clutch type will make a difference. Eaton never warranties a posi where synthetic oil was used, steel clutches or the new Fiber type.

[Mark F.]

Thanks, Gary...

With today's reverse engineering and analytical technologies, you'd think the old whale oil chemistry could be replicated...

...and maybe it has been ?

[Patrick H.]

Thanks, Gary...

With today's reverse engineering and analytical technologies, you'd think the old whale oil chemistry could be replicated...

...and maybe it has been ?

I think we're way beyond that.

For Mark, the modifiers in oil do separate out over time. That 1990s oil may be useful only for display at this point.
If it were me, I'd buy new.

[Mark E.]

I think we're way beyond that.

For Mark, the modifiers in oil do separate out over time. That 1990s oil may be useful only for display at this point.
If it were me, I'd buy new.

That's bad news. I still have 5 bottles of the gear oil and 4 bottles of the additive.