Recommended fluid type for GM transmissions

[CPT]

I get asked quite frequently about what transmission fluid we recommend for the GM transmissions we build. The answer used to be a little more simple... Dexron III / Mercon. However, GM no longer allows oil companies to use the word "Dexron". Most companies have switched to calling it "multi-vehicle" fluid. Oue experience has been that we've seen no benefits from using synthetic fluid in a 4L60E, 400, 350, 700, 4L80E, 2004R, etc. Now, if you use a particular synthetic and you're happy with it, then there's nothing wrong with it. It's just that you're spending more money than you need to. As far as brands go? Most fluid comes from the same place and put in bottles with different names. Parts store brand fluid will work just as well as brand name fluid. The only thing we tell everyone not to use is really cheap fluid or recycled fluid. Cheap fluid is usually easy to identify because it has no dye in it to give it the pink/red color.

NEVER, under any circumstances put any additives in your automatic transmission! Most additives are nothing more than repackaged brake fluid. Stuff like Lucas will break down the rubber seal and turn them into a gelatin type substance. Once that happens, they will disintegrate. Lucase swells the rubber seal. This is how it "stops leaks". When we take a trans apart that has had lucas in it, we have lip seals on the pistons that are gooey and hanging off the pistons. The seal is supposed to fit tightly into the groove in the piston, but after Lucas, you will have a piston with a 6" diameter, but a lip seal with a 7" diameter.

[96LT1355Z28]

Sticky? @popo8

[Dan Jaeger]

Any suggestions for my 93 m29/t56?

[CPT]

Sorry, Dan. I only build automatics. I'm not sure what to use in a stick.

[firebird_1995]

Any suggestions for my 93 m29/t56?

Not 100% sure on the m29 but the later year t56's were dex/merc 3 I believe

[Dan Jaeger]

Alrighty, just figured I'd ask, she needs a flush and a new rear seal. Appreciate the info and the response anyway.

[NoMoneyZ]

The side of my 1995 t56 says dex II, yes as in 2. Not a typo. At the GM dealer I work at we put dex 6 in em.

[96LT1355Z28]

I've used store brand Dex 3, until now (10 years of race seasons) without any issues. Switched to Redline shockproof light weight gear oil this season but that's for the faceplated gears.

[popo8]

Sticky? @popo8

Done.

[audiorailroad]

hey frank what if the synthetic is mostly clear/tannish color?