i have had my tires balenced and i have had my spark plugs changed i still feel it.

 

Could be an unbalanced drive shaft, could be bad u joints could be....could be.....get where im going with this? You need to be a lot more specific with the problem. When your driving does this usually happen at speed or rpms or is it from the second you touch the pedal? What rpm/speed does it happen at? Can you pinpoint what part of the car its coming from? Sometimes with a vibration it can be really hard to pin point because the vibration will carry right through your whole drive train so it can seem like its coming from your rear end when its really coming from your engine. If your not completly sure flip it into neutral and rev up your engine and see if the problem happens. If not its probably not engine related (although the problem sometimes even if engine will only show up under load so if it doesnt happen it doesnt mean 100% its not engine but if it does you know it is)and we can start looking for the problem elsewhere. Give far more detail into the problem please or you wont get any useful help.

 

definitely a lot more information...we'll help you narrow it down

 

i reved it in neutral it feels better after i put plugs in, may be its a drive shaft its a 90 iroc z with a 305 has 131000 on it. I can feel it most about 65 to 80 mph i have has three diffrent sets of tires on it now, the dash abd the sterring wheel just vibraet

 

id get your drive shaft checked for balance just because but i doubt thats the problem....maybe its an engine mount? if thats about to go itd give you some good vibration but im not sure what else it could be doesnt sound like anything too major....When you are running tests and posting the results be as specific as possible...ie at 3500 rpms in neutral the vibration first starts i feel it through this first blah blah blah because the more info we have the better we can help. Also remember you have a chevy v8 under the hood youre going to get some normal vibration.

also questions about your test...when you had it in neutral and got the vibration does the vibration feel any different then when the engine is under load (in gear).

 

the vibrations in nuetral starts about 1000 rpms and smoths out at 1200 or 1300, that could be a fly wheel that is messed up i have had three transmession and nobody has checked it

 

Could be the bronze bushing in the fly wheel, is it new?

 

no havent