i have an '84 GSL-SE with a shitload of miles on it that has several clunks under the car.

are there any common things that will whack against the underbody of the car that i should look at? i think the first think i will do is replace the transmission mount, as i seem to have a little bounce in the drivetrain. i suppose this is a good place to start, no?

 

Anything rubber. Trans/motor mounts and suspension bushings are the most common.

Get it up securely on jack stands with all 4 wheels off the ground. Give everything a good strong tug, if it moves then check it out a little closer.

 

Front-end stuff to look for (from my own experience on my 84SE);

Front lower control arms have a rubber bushing at the inside that will get torn up over time and miles. The stock Mazda replacement bushings come with the lower arm, and on top of that, you get a new outter balljoint at the upright, too. Good investment, since this really tightened up my front end and restored the driving comfort overnight.

Radius arm bushings - from the front airdam, you can see these that are mounted on the radius arms under huge washers. Replaced with poly bushings and now run very quiet and with very little front/rear deflection. Stiffens up the front of the car considerably.

Idler arm bushings - cheap and easy to replace, restores steering feel and possibly wheel alignment, which may cause steering problems and strange tire wear.

Engine mounts - easy to change in about 1-2 hours with the right tools. Combine with rear tranny mount if you have the time and energy.

Not suspension related but,... door seals - the rubber welt seals help to center the door in the frame, and a lot of clunking was coming from my doors and window channels banging back and forth under movement. This was possibly the single biggest improvement to my ride comfort. Hard to believe.

Get the front end up on stands and you should have a good view of what needs to be changed out or rebuilt. HTH,