RB20det harmonic Vibration. 2600 rpm

[geartech]

I'm trying to isolate a harmonic vibration in my rb20 s14. I'm leaning towards a harmonic dampner but the car also has the yellow poly mckinney mounts. I have the softer rubber units to put in but I dont think it will make it much better. Is there issues with the 20 dampners? or any other ideas.

[Yellow4g63]

Is this free reving or driving? if it's driving might be drive shaft related.

[Coolwhip]

+1 for the free revving or driving.

If it comes down to replacing that 17+ year old balancer, let me know

[geartech]

My bad, I should have mentioned that it will do it free rev or while driving. I can push the clutch in and let the motor come down to idle and the vibration dissappears. I can free rev the motor to 2000 ish and the vibration will build and the subside as it pass thru that rev range and it will begin again at a higher rev point but I don't remember what range above the 2600 it starts again.The more I think about it I'm thinking harmonic dampner.

[Coolwhip]

as suspected, free revving eliminates the possibility of a drivetrain imbalances. Unless you have internal issues (in which would most likely be accompanied by some kind of knock or slap) you probably can narrow it down to the balancer.

[geartech]

Fixed it. It was the Mckinney poly motor and trans mounts. Both poly motor mounts were broken. replaced both of them with the rubber mounts. WOW what a difference. All the harmonic vibrations are gone. Now all I have left to straighten out is the idle. It seems to stay around 1300-1400 rpm. I'll try to get some pics of the poly mounts to show the failure, they aren't the best built mounts I've aver seen.

Thanks for all the input though. Now I actually enjoy the car.

[raremotive]

Ricky,

what are your plans for black friday?

[Coolwhip]

Hey Darren... no dinner dates as of yet... you paying? HAHA just playing.

I don't know, if any, perhaps some imput from the masses would better direct my thoughts.