It's unclear to me what the more generic spec for my car's manual transmission, the Tremec TR6070, actually is. The owner's manual says to only use GM part #88861800 which is labeled as "manual transmission and transfer case fluid". I *believe* it's DEXRON III though there was a TSB saying that name has been phased out in favor of this less-useful product name. This makes it a bit challenging to find an alternative in the aftermarket.
Red Line says to use D4 ATF, Amsoil says to use the Multi-Vehicle Synthetic ATF, Motul says use their Multi ATF, Royal Purple says use their Max ATF, etc. A quick glance at the technical data sheets for these products indicates KV@100 of ~7.5, KV@40 of ~37; the GM fluid's datasheet shows 7.7 and 34.26, respectively. I don't know if the OEM stuff is even synthetic since the MSDS says "lubricating oils (petroleum), C15-30, hydrotreated, neutral oil-based".
The confusing part is that these ATF fluids appear to be very broadly-compatible and meet a zillion different OEM specs. All of my previous cars made it simple and just said "75w90 GL4" or whatever.
So, is the answer simply: any fluid that's approximately KV@100 of ~7.5 and KV@40 of ~37?
Red Line says to use D4 ATF, Amsoil says to use the Multi-Vehicle Synthetic ATF, Motul says use their Multi ATF, Royal Purple says use their Max ATF, etc. A quick glance at the technical data sheets for these products indicates KV@100 of ~7.5, KV@40 of ~37; the GM fluid's datasheet shows 7.7 and 34.26, respectively. I don't know if the OEM stuff is even synthetic since the MSDS says "lubricating oils (petroleum), C15-30, hydrotreated, neutral oil-based".
The confusing part is that these ATF fluids appear to be very broadly-compatible and meet a zillion different OEM specs. All of my previous cars made it simple and just said "75w90 GL4" or whatever.
So, is the answer simply: any fluid that's approximately KV@100 of ~7.5 and KV@40 of ~37?