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1966 riviera th400 trans fluid


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I would avoid Dexron VII if Dexron III is available.  Dexron VI is synthetic based, which is fine, but it is somewhat thinner viscosity and 'slipperier' (if that's a word) then Dex III.  For example, the transfer case in my '04 Silverado calls for ATF, which would have originally been Dex III.  When I changed it and filled it with Dex VI (thinking it would be 'better') it stopped allowing me to shift 'on-the-fly'.  The slicker fluid isn't compatible with the synchronizers.  So, I'd be similarly concerned about the friction material used in older transmission clutch packs...

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If you can find Dex III that's what I'd go with, for reasons EmTee stated above.


This question comes up every so often on an Olds forum I frequent, with predictable debate. One 40-ish transmission builder says the worst new fluid formulations are better than the best that were available when T400s roamed the earth. I strongly disagree because modern fluids are designed with different friction and detergent properties than the old formulas were.


For some reason that boy can't wrap his head around that, even after a couple of people had serviced their older WORKING transmissions with synthetic fluids and then the clutch packs slipped so much the car wouldn't move.


There's rumour the Japanese still have a dirty little secret in their transmission fluid formulas. Something called whale oil...

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Can snake oil be substituted for whale oil?

Or you could wait a while, convert to an electric motor and not need oil. 

It's like having a 3G phone that is obsolete when they go to 5G..... what's and old-timer to do?

My daughter drove 89 miles in her Tesla but used 124 miles of her range, nothing is simple anymore. 

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4 hours ago, rocketraider said:

Something called whale oil...

Real Whale oil is easily detected by its odor. 

This may only be true if its 60 years old.

Found some in a couple of antique outboard gearcases.

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