Best transmission fluid for old transmission

[Steven37]

I'm changing the fluid out of my old th350 what would you guys recommend using?
https://www.amazon.com/Valvoline-DEX...rds=DEXRON+III
I was just going to pick this up.. Think its a good choice?

[cadillac_al]

The tranny won't care too much so just about anything will be fine. I don't know why it costs so much at amazon. Walmart has a few kinds for $3-6/qt. I've been buying Super Tech Dex VI for years.

[Dead Parrot]

If you have a Sams or Costco membership, check there first. And their damaged section. Picked up an unopened case of 12 quarts of Sam's store brand Dexron III for under $20 because it had some oil spilled on it.

Think the regular price for the 12 pack case is less then what Amazon wants for that 6 pack.

[hatzie]

The new (in 2006) Dexron VI is compatible to use in most GM Automagic transmissions. I use it in my TH400.
If you purchase a GM rebuilt 4L80E, 4L60E, or 4L60 the paperwork will recommend Dexron VI. The latest GM TSB recommends Dexron VI in everything but the early 2 speed automatics, manual transmissions that called for Dexron, some power steering systems, and transfer cases that called for Dexron.

BTW: There is no such thing as Dexron III unless you have fluid that was bottled in 2006 or before.

[rich weyand]

I switched to full-synthetic ATF when I got the truck, and shifts got crisper and engine temperatures dropped. Since they share the radiator, I assume that means that transmission temperatures dropped.

[Dead Parrot]

Went back and looked at the box I picked up from Sams. It says it is for applications previously served by Dexron III/Mercon. Guess that is what I remembered seeing. Works for a 75 TH350. The box still had the damaged merchandise override sticker on it. $15.03 for a box of 12 quarts.

[hatzie]

Unfortunately "for applications previously served by Dexron III/Mercon" doesn't mean it's the same formulation as Dexron III. It's probably close but there's always the temptation to make it cheaper and without the GM licensing there's no oversight. As long as it takes 20,000 miles or more to damage the unit they will not get successfully sued.

At this point good fluids that are likely truly Dexron III compatible, made by reputable oil firms like Mobil and Valvoline, are more expensive than Dexron VI. You can tell right away that one of the Mobil ATF formulations is the real deal because the bottle states that it's tested to be compatible with GM 88861800 manual transmission fluid that GM says should be used in applications like the NP208 & NP241 that called for Dexron II or III.
The inexpensive Walmart Supertech brand Dexron VI is $4.30 a quart. I just put 6 quarts of it in my 4T65E-HD. Since anything with Dexron VI on the bottle is licensed and tested by GM it meets the standards to be called Dexron VI.

I use Dexron VI in my 1986 TH400 (3L80) that originally shipped with Dexron II-D & my 4T65E-HD that shipped with Dexron VI. Zero issues. Dexron VI will work in the Turbo Hydramatic transmissions from the 1970's on. For us that means the TH350, TH375, TH400 (3L80), and TH700R4 (4L60)... and maybe a TH200R4.

I would not use Dexron VI in the antique 2 speed Powerglides or the Hydramatic transmissions from the 1950's and prior but there are alternatives that mimic the whale oil Dexron fluids for those antique GM automatic transmissions.

[Dead Parrot]

Went back and checked the various Dexron bottles I have. Interesting. Here are the condensed details for those interested. Some of these bottles may be several years old.

Coastal Unilube : Claims good for applications requiring Dexron III, IIE, IID, Dexron, Mercon, Ford M2C116-H or M2C138CJ. GM approval - F-30310, Ford Approval M940408.

Stuff from Sams : Claims good for Dexron II, III, & Mercon. Do NOT use in GM vehicles after model 2005 or Ford after model 2006. Not for Type F, Mercon V or Dexron VI applications.

O'Reilly : Claims good for Dexron IIIH, IIIG, IID, IIE, Mercon, Type CJ, Type A, Allison C-4. Also not for GM after 2005 or Ford after 2006 and not for Type F, Dexron VI, Mercon V, or Mercon SP.

SuperTech (Walmart) : Mercon V label, Claims good for Dexron III, II, Honda Z-1, Mercon, Nissan Matic-J, Toyota T-IV. Not for Type F or CVT transmissions. (Oddly, no warning about later model years.)