Help!...My 83 Automatic will idle fine when park @ 800rpm..But as soon as i put her into Drive or Reverse,the idle will drop to around 500 rpm and she will shake like a diesel...Can anyone tell me what to check?..Tks in advance!

 

I had an 83 S-10 that would shake like that when I put it in gear. It was a busted tranny mount and engine mount. Don't remember if it idled low as well that was about 12 years ago.