1st-2nd sloppy shifts in '05 Auto

[Chiron]

For a while, I noticed I was having really sluggish shifts between 1st and 2nd. So, 6 months ago I got a tuner to hopefully alleviate the problem. No such luck. The tune was from Eric Brooks for my '05 GT Auto w/ zero additional mods. We went back and forth, trying to see if it was an error in the tune, troubleshooting various things to no avail. After some time, I gave up. I returned my car to stock tonight to load a new tune later this weekend and noticed it was still doing it. The rest of the shifts are noticeably firmer than 1st-2nd. Is something wrong with my tranny? I know next to nothing about these transmissions. Is there a synchro that's notorious for crapping out other than, I think, 3rd? Anything I can do to troubleshoot?

 

[TexasBlownV8]

The intermediate servo may be worn out. What mods do you have, mileage, prior service/maintenance on the tranny (fluid/filter), etc.

 

[Chiron]

For the duration of this issue, the car has been bone stock, save for some Flowmasters. Right now, I'm sitting at 103k and some change. I bought the car with about 70 grand on the odometer, and I don't know anything about previous maintenance. I planned on doing a 100k mile tune-up in the near future, but I personally haven't done any work to the tranny.

 

[TexasBlownV8]

Sounds like the 1st-2nd bands are possibly wore out as well.
Is it slipping, when trying to shift, if you can tell?
Probably going to be time for a rebuild.

 

[Chiron]

I'll try and describe it to the best of my ability, but a video of the tach would show it all. Basically, at WOT the car will climb to 6 grand and sort of "hover" for a second, then it'll shift. The rests of the shifts are fine, but 1st-2nd kills me. I figured it'd be time for a rebuild, or just finding a new tranny from someone. I can't afford to have much downtime with my car. Would it be cheaper and easier in the long run to find a tranny, take it to get rebuilt, and then swap it out myself? Or should I just have a tranny shop rebuild it in the car? While I'm in there, I may as well throw in a higher stall, I'd imagine.