got a few weird vibrations in the car that i can't seem to get rid of and was wondering if anyone has any ideas.
there is a vibration at 800-1000 revs and one at 1300-1500 revs. you can feel both through the seat and both get worse the more load is put on the engine ie increase the throttle the vibes get worse. It seems to have the worst vibrations in the middle of the rev ranges it occurs at, so it is worst at 900rpm and 1400rpm. As a side effect of the vibrations there is a metallic rattle in the back at 900rpm and the gearbox/shifter rattles at 1300rpm. This has happened ever since i chucked a manual transmission in the car. the noise at 1300rpm has also changed since i put a different engine in it, it was become louder and occurs at a slightly higher rpm.

These are all related to engine speed and engine load not road speed. The engine mounts have been replaced at the same time the gearbox was put in. One of them was even totally broken and didnt make any vibrations before putting the manual in.
I have tried a different harmonic balancer which made no difference. i have tried a different gearbox mount which also made no difference. The exhaust doesn't seem to be hitting the body either, but it doesnt have the hanger near the cat that connects to the gearbox if that even makes a difference. So basically i'm fresh out of ideas.

might be the flywheel out of balance .thats all i can think of

Yeah might be the flywheel, that's the only thing that makes any sense. I know that about 5 of the theeth on the flywheel have had about half of them sliced off. Would that realy cause any problems though?

That cat to box hanger you are missing, when mine was loose as it made a horrible rattle at a few different rev ranges and shook the car.
So it'll either be that or you're flywheel. Did you get it re surfaced before you put it in?

i didn't have the flywheel resurfaced originally but got it done when i put the new engine in the car. The vibrations are a fair bit worse since.
I'm gunna try fitting the gearbox hanger off another ED to mine to see if it makes a difference, but the car i removed it from doesnt have any vibrations since removing it.

Fly wheel bolts loose or broken.
Harmonic balancer.
Gearbox mount.
Good luck.

Got another idea what it might be. It says in the workshop manual you're meant to allign the clutch plate with the flywheel in a certian orientation. The flywheel isnt symmetrical as it has holes drilled in one side and some paint should be on the the clutch plate which faces opposite the holes. But i have an xtreme clutch and i don't recall any markings on it or installing it a specific way when i put it in. So it could be the wrong orientation. would this cause those sort of symptoms though?

Deffinantly could.
How's your harmonic balancer?