'67 Camaro E/SA redo

[HandOverFist]

Once again, no good news to report. Arrived at the track this afternoon with high hopes, but I was foiled again. I'm fishing for answers so let me set this up in chronological order.

Half way to the track my partner calls and tells us to make sure we check the transmission fluid level when we arrive. We had none in the truck so stopped at a auto parts store and picked up a quart. My buddy comes out and said they had no Dextron 3, so he bought what was available which was Dextron 6. I thought to myself no big deal.

Unloaded the car and ran it up and down the return road to warm everything up. Shifted fine and I stalled the car a couple of times noting nothing irregular. Pulled up to the trailer where my buddy is waiting to check the trans dipstick level...finds it low and puts about 3/4 of a quart in the transmission. Good to go.

After gearing up I pull the car into the staging lanes prepared to make a pass. My buddy is standing beside the car while I do my normal 1-2 shift burnout then ease forward. When stopped I put it into first gear and ease into the beam...stalled about 2700rpm I bump in and the lights come down. Nailed the throttle and it sounds like it blew the tires off the car...not sure what just happened I shut it down. A track hand looks under the car and says no fluid spilled. I restart and back the car into the oval track for a closer inspection. We talk for a moment and he says the tires never turned at the hit....hmmm. I back the car further into the oval track and try first gear again...it barely wants to pull the car. Second, third and reverse gear seem normal.

I ease the car back to the pits in second gear. Got under the car and check the cable adjustment which is dead on correct. We load the car and come back home still not sure what the problem is. While unloading the truck I grab the nearly empty bottle of transmission fluid and it catches my eye...that quart of fluid is a full synthetic. We use Dextron 3 in this transmission.

Question : Is it possible this was a self inflicted wound? Could a quart of synthetic fluid cause this metric 200 to slip that badly in first and have no apparent effect in the other gears? I'm going to pull the pan in the morning and check for any debris, but I can hear no odd noises coming from the transmission when running. I'm sure Thomas Arnett could say what it is off the top of his head, but it will likely be Monday morning before we talk.