1980 Chevy El Camino 305 Auto trans stall issue

I have finally gotten my El Camino running. I was able to take it for one spin around the block after adding trans fluid ( figured out that that you are supposed to check trans fluid when the trans is warm) at any rate after adding the appropriate amount of trans fluid it now stalls out when put into gear. We tried it into reverse and first same result. What is happening? What is the idle speed of the engine? If it is too low, the transmission will stall the engine out if put into gear. Which transmission do you have? Sorry it has taken me so long to get back on this. I am not entirely sure which trans it is. Is there an easy way to find out? As far as the idle speed we did increase it to handle the problem but we had to increase it way beyon anything reasonable to stop the stalling. When the engine is idling out of gear how is it running. Doesn't it sound like it is running rough or missing? Are there any modification to the engine? Does this happen all the time or when the engine is hot or cold? If it is in stock form it should have a TH350 or TH350C transmission. You can tell if it is a TH350C if you see square plug on the shifter side of the case. If it is a 350C, there could be a problem with the torque converter clutch staying engaged. if the tranny has a lock up converter the converter may not be unlocking and causing engine to die and if so you should be able to unplug it and see if it still stallsCar Repair Talk's forum.