1966 C6 tranny fluid help

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BlownM3
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1966 C6 tranny fluid help

Post by BlownM3 »

I am doing a transmission swap with a transmission that I got for a wrecking yard from a 1966 Lincoln. Not sure if the transmission was ever rebuilt but I dropped the pan and the fluid looks great. I have done some research and it appears that this car originally used Type F. Is this correct? I am installing a brand new converter as well. Will I be OK if the whole system is flushed and I used Mercon? Or do I need to flush and use F? I know that a rebuilt tranny can be used with Mercon but what about one that still has original clutch packs? Whats my safest bet?

Thanks
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Dan Szwarc
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Re: 1966 C6 tranny fluid help

Post by Dan Szwarc »

Original Fluid is Type F. All rebuilds should use Dexron III fluid (as you said).

However, there is no simple way to know if a transmission has been rebuilt from the outside. Some mechanics will mark the transmission in some way. Some paint the transmission (never painted from the factory). Inspection of the clutch packs is the easiest way to tell. An experienced rebuilder will know what modern clutch packs looks like compared to originals.

It's been discussed about whether or not one could try mixing a small amount of the transmission fluid with a sample of Type F and a sample of Dexron and look for a reaction (like bad mixing, separation, etc.). There may be a specific gravity measurement.

If you want my opinion (too late), I can almost guarantee that if the car has over 50K miles and has been driven much in the last 10 years, the transmission was rebuilt. The original seals would be dried out by now and the car wouldn't drive well. It's been 49 years!

While there are still some out there with original transmissions, the good ones get enough exercise each year to stave off the hardening of the seals with just enough use. Others are likely due, but the owners cling to their originality.

If the transmission is out, open it up and inspect the clutch packs. You're already 95% there.
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