Originally Posted by kerry edwards

Here's my hypothesis. It's shifting worse now because you're using your heater and there is a vacuum leak somewhere in the climate control system. Try turning off your heating system and see if shifting improves. I'm not familiar with the 87 climate control but I'm guessing it's the far right button on the climate control. It's the simplest vacuum test that requires no guage or mechanical savvy. Report back the results.