I have an '84 Z28 that won't move when when I put it in drive or reverse when the wheels are on the ground. When I have the rear axle on jack stands the wheels do turn when I put it in gear. The transmission is a TH350 and the engine is a 350 sbc. The torque converter and flex plate are attached and I have fluid in the transmission. I took the back off the differential and everything is intact and looks like it is in correctly. I'm able to roll the car in neutral. Any ideas?

 

Your transmission isn't working

 

very low on tranny fluid will cause that-try pouring some more fluid in and see if it starts to work.If dipstick shows correct level with engine running,could have wrong dipstick.

 

I'm thinking the transmission is bad. Added a bunch more fluid and now it will go into reverse, but I don't want to back through the wall of my shop so I haven't tested it. It creeps forward in drive but only if I have the rpms way up.