hi, I'm Zac and I'm new here.
My wife and I recently bought an 84 300td with 166K on it. Yesterday we were starting the car and in park it wouldn't start. The battery power seemed fine and the glow plug light was coiming on ok. I moved the shifter around and when it was in drive it started right up like normal. On the way home we stopped at the store and I left the car running. I went to put it in park and it was slipping and rolling down the slight grade in the parking spot, making a clicking noise like it was trying to "catch". Any ideas what this might be. It's making me very wary of its reliability.

thanks in advance for your help.

zac