My 1990 Integra seems to shake everytime I shift gears. The motor shakes I believe. If I shift and let go of the clutch fast then the motor seems to shake. If I shift gears and slowly ease off the clutch then it doesn't shake at all. What could this possibly be? Also the clutch seems very light. I heard theres a way to adjust the stiffness of the clutch. How do I adjust this?

 

Have you checked the condition of your motor mounts?

 

^^+1. check motor and transmission mounts

 

Motor mounts seems fine. Anything else? I'm worried that it might be a transmission problem.

 

Still a cable transmission?

If so, there's a **** on the clutch cable that can be used to adjust the clutch. It sits in a bracket mounted to the transmission. Looks similar to vin diesels nos ****. Lol. I know we've all seen that movie.

 

how did you check the mounts? because a simple visual inspection is not enough to know

 

Have someone try to take off in first while pressing the brake also, have the e-brake all the way up as well, a block or something to chock the rear wheels is a good idea too. While they try to take off in gear the motor should rock a little bit don't stand in front of the car while checking. that should point you in the right direction.
Are all the motor mount bolts nice and tight? anything stripped?

 

you can also put it on the hoist and pry at the mounts with a large pry bar. see if there's any play. pry in all directions

 

Could also be an axle problem.