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first gear stick

My trans has been having problems for a couple months. So I took off the pan and there was no crap in it or on the magnet. What it is doing is that it drives normally just fine and also under moderate accelleration. When you nail it, it gets hung up in first gear and then the rpm's fly up like it went into neutral and then it slides into second. I went and talked to the local trans man, and he said that if there is nothing in the pan my converter is probably wasted. Also, when I went to the track I brake torqued it up and something just gave and the drag radials didn't budge but the rpm's flew up like in neutral. So I called Bruce and got a converter. I put it in yesterday and nothing changed. My question is-what else can I check before rebuilding the trans and emptying my wallet again. I am not an expert on adjusting the throttle cable, so give me some tips on that. Thanks alot!
also I forgot this-six months ago I put in an art carr shift kit. It would bang into every gear pretty hard and always bark second no matter how much accelleration. I was told that this is normal and that it couldn't hurt anything. But guess what-when I started having all these problems it wasn't even thinking about shifting hard, and once again there wasn't any crap in the pan?
Sounds as if the aggressive 1-2 shift was a bit much for the band and the anchor hole stretched on it. That would put the band out of adjustment causing the bad 1-2 shift.

There would be no resulting trash in the pan luckily, but the only remedy is to remove the transmission for repair.
I Bet

I'll bet it is the sprag. Does it go in manual low?
If yes, then sprag is gone... If no...
Does it move in reverse? If the answer to that question is no .... you broke input shaft , forward drum shaft , or stripped the planet off or broke od ring gear splines.
Does it have line pressure? if no pump internally exploded but I would think you would have had trouble getting converter in.
(BTW , thanks for your patronage:))

Thanks, Im yanking the trans to rebuild it today. $$$$$$$....