1989 Astro

Ok, a little quickie here. My 89 is having a little problem. When I crank it up, it has a really rough knock. If you rev it, it knocks harder. ( I know, I shouldn't rev it, but at the time, i was mad). But when you put it in gear, it won't knock. So, I am hearing that it's the rear main. But I was also told it can be fixed by not pulling the motor. Am I looking at being able to just pull the pan? Thanks for any help!

A bit more background on the knock might help with diagnosis. It might be something as simple as a bad motor or transmission mount. Post a little more data on your '89. Like mileage, recent maintenance, sensors that have been replaced, last tune up etc.