Help me pick Trans Fluid for '89 Firebird

[SpeedRacerX]

OK, I have to drain and change the fluid on my son's 1989 Pontiac Firebird Formula 350, with TH700R4 Auto Trans.
Car has 30,500 miles but it has been sitting for about 12-14 years so the fluid needs changing.
Trans has B&M shift kit and 2800-3000'ish Stall with about 10,000 miles on it & whatever fluid is in it.

Normally, I would leave this alone but given the number of years that have gone by and after seeing & SMELLING what became of the motor oil after 15 years, clearly, time has an effect on these fluids and they should be changed to be safe.

I've gotten GRRRR8 pointers from Charlie but of course, for some reason, finding exactly what I need in fluids & parts in my area seems to be challenging.

I am opting to drain the fluid, change the filter, and fill 'er up VERSUS a complete flush as I've heard about the nightmares that can happen with a flush and particles getting stuck in bad places leading to slips and hangups.

Owners manual called for Dexron II (old I know - LOL).

I was told that Dexron VI is a good safe way to go BUT I have also heard good things about Royal Purple Max ATF (synthetic) and Amsoil ATF (synthetic). I am having a hard time finding a good Dexron VI near me, I can't find the Amsoil, and the Royal Purple is expensive but if I have to use it, I will.

Any thoughts on which of these you would recommend - Dexron VI, Amsoil, or Royal Purple???

My goals would be safety and compatibility for the Trans PLUS lower trans temps. Trans temps takes forever to rise but eventually hit 175, 180 and then slowly climb to 185, 190 and barely, if ever, reach 200. Has a remote-mounted transmission cooler that helps. Fresh fluid might help the temps too.

One other question: does a gasket go back on the Trans pan OR just some RTV?

Thx!

[todds87ss]

RTV does not (in my experience) seal a trans pan real well. Always try the gasket.
I'm not a fan of amsoil nor RP. I'm sure that they make great products, but Regular Dex 6 should be fine.
I'm not sure any fluid will lower temps. They all likely have similiar specific heat capacities. If you want lower temps, use a larger external cooler, and run it after the radiator cooler. Or try a larger pan.

[BMR Sales]

When I worked in the transmission shop we would use the Dexron III/Mercon for all our 700R4/4L60E transmissions and we never had an issue. Most of the transmissions we built were performance rebuilds and everybody wanted to put some kind of magical fluid in it when in reality it is a big waste of money and no better than the store brand fluid at your local auto parts store. Like Todd said you I doubt you will really see a change in transmission fluid temps from changing the fluids but if you are staying 200 degress or less you are doing well and the cooler is doing its job. Don't use RTV for the transmission pan, first of all it is super messy and second of all if it comes loose it can create clogging issues. I am not a big fan of the cork gaskets because they have a tendancy to split if over tightened but most kit you get from the store will have them. If you can see if you can paper/fiber based gasket instead.

[G8GTSBM]

This is what I'm using and It's GM approved. http://www.oreillyauto.com/site/c/detail/VLV0/DEXVI/N0471.oap?ck=Search_N0471_-1_-1&pt=N0471&ppt=C0207

[John@AutoAgenda]

I am running Dex 6 in my fully built Stage V trans with Edge converter and also have an additional trans cooler and live in the desert and have had no problems with extreme temps at all.

[SpeedRacerX]

Great info guys! Thank you.

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

[todds87ss]

When I worked in the transmission shop we would use the Dexron III/Mercon for all our 700R4/4L60E transmissions and we never had an issue. .

True. You could save a ton (4.00 or so a quart) by using Dex3.

[SpeedRacerX]

I picked up the Valvoline Synthetic Dex VI, trans filter and new gasket.
I also picked up Royal Purple Max Gear (doesn't need the additive for limited slip) for the Rear Diff and a new gasket. Oh and that handy dandy pump and tube that goes on the gear oil quart bottles since tilting and squeezing isn't an option in this area. LOL.