shake when in gear at a light

i have a 97 sl2 5 speed manual trans.and when im at a light sometimes the car shakes like crazy.i mean vilantly.but if i take it out of gear then its fine.only if im in gear.and it does this about 50 % of the time.
i replaced my top engine mount thinking that was it.it was not although that mount rubber was splilt almost in two.that helped for a lil bit but still does it.so any one ever have this problem and fix it.

dont hold clutch in at a light, it causes problems to the engine. it sounds like either your bottom end on the engine is about done, or clutch isnt fully disengaging.

i dont think its the engine,my engine sounds smooth.and runs smooth.only has 70k miles on it.my car runs fine,just when i put in gear sometimes makes a clumpin sound and shakes vilently.i did some reasearch and here that it also might be the hydraulic clutch systems.so i am gunna change mounts and that system and see what happends from there

it is very rare for the dog bones to be a problem, but it does happen. the bottom trans mount usually tears causing a bit of vibration. i fixed my bottom trans mount by getting some extremely strong construction adhesive, sanded and cleaned as much as i could in, glued it, and then filled all around it with polyurethane.

but yes it could be due to clutch hydraulics. i wasnt exactly saying its the clutch, but it could be that its not fully disengaging. but understand, which im sure you will find before you read this, the hydraulic system is one piece and cheapest can be found is about $120.