I just changed my fluid yesterday and want to change it again (since theres still old fluid in the torque converter). Search but with no posts, what in your opinion/experience is the best additive to add to a 700r4 tranny with ~150,000 miles?

Lucus...

I believe thats lucas and i will be buying me a bottle...

Nothing

Why nothing? Im trying to prolong the life of my transmission by adding the best additive and prevent leaks. Nothing will do nothing...

Yes, and nothing will do the same thing as any additive you put in, but costs less.

So lucas wouldn't do anything, I need one more opinion before I decide.

b&m additives

I used lucas b4 and tranny started to leak later.

The number one way to make your trans live longer is to make it run cooler. Trans coolers FTW!

how does it work with a trans cooler? since theres already one on the car going into the rad

external cooler.

basically a mini rad for your tranny that mounts infront of the radiator. You just strap it on, hook up the lines in series with the cooler in the rad (helps to get tranny up to temp faster and keep more constant temps) and your good to go.

sounds like something to invest in...

the cheaper tranny coolers are worth not much more than a bottle of additive too!

whats a good one to invest in? i already put a nice aluminum aftermarket in the car for the radiator, want something that will work well with the system i have.

Just about anything will work. The B&M coolers are good, probably the only good product B&M sells.

Lucas is a good product if your trans. is on its way out or has pressure problems, it seems to keep it going longer. If you don't have either of those problems, I'd say don't add anything else.

either a nice tranny cooler
or the derale pan

and constant fluid changes
making sure not to overheat the tranny