After seeing an old video in which Scotty recommended AT-205 in transmission I want to add it to my 2006 Z71 Chevy 1500 Suburban, 5.3L with 230k. My transmission has never been serviced and noticing some intermittent hard shifting lately. I want to maintain my transmission as best as possible so will adding AT-205 cause any issues with slipping? Thank you!!! 
will adding AT-205 cause any issues with slipping?
Probably not but it's not going to help hard shifting either. That's not what it's for.
If your transmission has never been serviced in 17 years and 230K miles it unfortunately is not likely to last a whole lot longer.
Okay, thanks for the good news. Lol.
At this point it's really best to just baby the thing and hope it holds up for a while, and plan to either have the transmission rebuilt/replaced, or replace the truck in the not too distant future.
I would not. At least the transmission still works right now. There's a good chance that if you put that stuff in, it will finish it off.
Yikes! I wanted to help my transmission - not ruin it. Lol. Any suggestions as to what else I might use?
Nothing. Start saving up to replace the transmission or replace the vehicle. 230k is already well beyond the average lifespan of these things.
Okay, since my Suburban is a treasure to me I guess I will replace the transmission. After all I have replaced everything else on it. Lol. Thank you!
AT-205 helps with leaky rubber based seals. It wont do anything for a transmission. If it starts to slip you can put lucas anti-slip in. But that wont buy you much time. Usually these transmissions last half that millage. Just take it easy
Okay, thank you.