Was wondering what everyone thought about this. All I can get in my area is the stuff from the Dealer, the Castrol or the Super Tech.

I have Castrol Dex V1 in my GMC truck and Valvoline Dex V1 in the wife's Buick. Both are working out real well.

go for the Castrol real good stuff a nice pretty red also Im running it in my S10

Castrol it is. :) I am doing a shift kit and tranny fluid change in the Buick in preps for a smaller supercharger pulley, tune, CAI and exhaust. :)

with the Dex VI in mine it seems to smooth the shifts out also.

That is what I have heard. Can't wait to do it tomorrow. The 4T65E-HD is an Ok unit, but with this fluid and
the kit it should firm up the shifts and give me prolonged life.
The car only has 65,000 miles on it.

oh yeah those 3800 S/C engines can be pretty mean

Cool..

Ended up going with the Castrol last night.
WOW! What a difference. The old fluid was 11 years old.
I was dirty but not burnt, no big metal piecer or anything funky in the pan.
Car shifts perfect. The shift kit really made a difference for the 4T65E as well.

Glad to hear it was a nice difference! I have ST Dex-VI and a DIY shift kit in my 99 Buick LeSabre with the N/A 3800 and non-HD 4T65. It shifts very nicely now!

I always hated the low line pressure for smooth shifts. I like to feel it. That way I know the clutches are not slipping.

What shift kit did you use? Got a link?

I got it from ZZPerformance, comes with an OEM filter.
Was EASY to install!
http://www.zzperformance.com/grand_prix/products1.php?id=570&catid=105
Got to my house in three days.
The whole thing took me about 2 and 1/2 hours [censored] around.

Nice. I also hate how these AT go into neutral and unlock the TCC when you lift off the gas and gives no engine breaking. That might slightly decrease engine wear (who cares AT usually wear out quicker than engines) and improve fuel mileage (AT cost more than a smidgeon of extra gas), but it can't be good for the life of the clutches and TCC. I guess the kit doesn't address this though?

Seems like with these ATs being electronic that an easier way to change the shifting firmness would be through the software.

Did you do a pan drop and refill or a cooler line flush out too?

With the 4T65 you can boost line pressure electronically too. The shift kit just does it for you, all the time. It also prevents/covers up the symptoms of a $500 repair if the electronic doodad fails.

The DIY shift kit only has 2 sizes of shims, a 1/2" long for the top 1-2 spring and 3/4" lengths for all the rest. I feel the shifts a little bit when it's cold, and it disappears as the transmission warms up, with the quick shifts remaining. Parts were acquired at Lowe's, LOL.