my 1986 IROC with an automatic Kicks whenever I put it in gear and use to when it shifted. It was a little low on fluid and when i filled it, it wouldn't kick when it shifted but still when it was put in gear. I checked all the mounts and the rear suspension, they were good. The only thing is the car never idles below 750, usually around 1,000. Is that too high and if so what should it be. What could be other causes. Thank you.

 

Mine did that, adjusted the kick down cable, and flushed fluid a few times and it has helped a lot. I even have smooth but crisp wot shifts now. But mine would shift smooth when hot. After cable adjustment but before new fluid.

https://www.thirdgen.org/detent

How to ajust your kick down cable, try that first.
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never mind, i just realized you have a manual, no idea how to fix, sorry.