92 Camaro Having Trouble Changing Gear

From your description, I’d have to say that your Camaro is about to undergo a major transmission failure. Certainly, I’d like to tell you that it’s a solenoid pack or maybe a blown sensor like the throttle positioning sensor. However, from your description it sounds like there are a number of things going on. Here’s a list of what I think may be happening:

1. The torque converter is on the way out. Though it hasn’t failed yet, it is likely about to start in the relatively near future. I am thinking this way because you said your Camaro pulled strongly even with the step-down hammer on. A failing torque converter will start behaving like this early on as it is no longer able to keep up with the demands of the rest of the transmission.

2. The turbine vans that are being fed by the torque converter are starting to wear, as well, and they are failing to keep up with the demands of the transmission.
3. One of more of the gears in the planetary train are slipping. Granted at this stage things are mostly engaged, but, they are beginning to slip and the tranny isn’t keeping up.
4. The bands and clutches are worn.

As you can see, there are a lot of possibilities. You’ve eliminated one of the big ones that I would have suggested first, checking the fluid level as you have already swapped it. There’s something I am wondering, though, the anti-slip additive you put it, is it recommended by the manufacturer? I am suggesting this because if you start working off page when it comes to things like the proper tranny fluid — like using an additive that may not be recommended — you may have also answered your own question.

I’d get another quick change of fluid and filter (don’t forget the stuff in the bottom of the pan) just to see if this doesn’t cure the problem. If it does you will be spared the $2,800-$3,200 expense of a rebuilt transmission. If not, then you are looking at a rebuilt transmission to solve your issues.