89 Iroc with the 350 and 700R4 all stock. I've been struggling with a poor idle quality, surging, and occasional engine stall and then surge forward when at idle. I've done all the engine checks and replacements on this site including timing chain replacement. It was quite strectched. Thought I was getting it as things seemed to improve but then all the good went away.
On one of my test runs the car when left in OD at WOT shifts well through 1-2-3.
Once into third the acceleration peels of around 75-80MPH but the RPMS hit 5000 rpm at about 85 or so in 3rd. It has stock 2.73 gears.
Another thing when I was dropping the pan to remove the timing cover my elbow touched the converter and it was too hot to remain their any time at all. Funny thing is I had let the car cool down to work on it. Engine temp was cold and the exhaust including the converter were too. I mean nearly outside temp. I'm wondering now if all of my problems are in the converter and transmission. Oh yes it's starting to overheat too which is odd Everything in the cooling system is new and works as it should.
Sorry for the length. My son and I are stumped on it at this point.

 

The 700R4 will not shift out of third and into 4th (OD) above 1/2 throttle. This is normal. If the run you describe took place 2 hours before working on the car, I can understand the converter&trans still being that hot. Check the operation of the torque converter clutch. Running on level ground in 4th about 65, hold throttle steady and slowly press brake pedal. Engine RPM should come up about 100 rpm before the car starts slowing down.

 

I think the tc being still hot is very normal.

for example, my TH-350...

I drove my car home at 5pm after a 5min drive from work so the engine barely warms up. at around 7pm i was ready to start installing my shift kit and to my surprise i got a hella burn from the splash. And after i had it all ripped apart with the valvebody out the oil dripping down from the clutch packs was still fairly warm which was around 9pm. Just to give you an idea how fast they build up heat and hold it.

 

Thanks
I think you are correct about the converter heat. My overheating problem was Kragen selling me the wrong water pump. It fit but didn't move enough coolant. Exchanged it and it's fine.

Back to the transmission. If I start in D from a dead stop with my foot buried to the carpet it shifts at 5000 from 1st to 2nd and then will not shift into 3rd unless I lift just ever so slightly. I'm thinking TV cable adjustment. If I accelerate in D from a dead stop with let's say 8/10ths throttle it goes 1-2-3 right at 5 grand.

It's actually 2nd gear it's stuck in when I mash it hard. I think I've seen this problem before on this site somewhere.
GW

 

I would try adjusting TV cable, It will most likely fix your shift point problem and if it is out of wack probably save your trans.