I have an 86 Wagon with manual transmission. Last night, I started hearing this clunking/knocking sound that seemed to be coming from the lower right wheel. I thought either I had a flat or that the mudflap was hitting the tire.

I made it my destination with just this sound. On the way back home though, stopped at a light, when I went to engage it into 1st gear, a big thump and rattle happened - it felt like something fell out of the front end. I was able to start moving in 2nd gear though it sounded very crunchy....third was a bit better and fourth was smooth.

What could this be? I'm worried it's something major. Clutch? Bearings? Mount? Synchronizer? OR the whole transmission? I need to get it to a mechanic but want to be knowledgeable on these symptoms.