So I just got a rust-free '79 242GT (hah that rhymes). In Ontario, that's a rare find. Its mostly in fabulous shape, but somewhere in the driveline it occasionally has an issue...I think either the clutch or diff. When starting out or going into second, it sometimes doesn't put the power down to the tires and makes a repeated clunking noise. If I let up for a second, its fine. My first thought was differential, but I thought the clutch may do that too if it skips for a second then catches and keeps repeating that. Is there any good ways to test which it is before I dive in and start replacing things? As a bonus question, if it IS the diff, is it normally the spider gears that die in them? Or am I looking at ring and pinion death? I hope its spider gears, because then i can just chuck a locking diff in there. Anyways, thanks in advance,

Nate Gundy