vibration problem

[beatshack]

Hi, I originally posted this problem in drivetrain tech, not knowing there was this auto-tranny sub category..

i have a 94 talon ES, automatic. for the most part it shifts and drives fine. at 3500rpm and again at 6000rpm i get a vibration that i can feel in the gas pedal, and also sounds like crap (like a cell phone vibrating on a table).. but only at those exact rpm and only when in gear... rev'ing in neutral is smooth all the way through.

any thoughts on what this might be?

 

[Awoler]

perhaps a balance shaft out of phase.....

 

[beatshack]

thx for the reply, a few people have suggested that now, so thats a good possibility

as i've never dealt with this problem before i will have to take it in.

 

[beatshack]

balance shaft pin was installed 180 degrees from where it should have been... installed properly now, and the car revs super easy and clean now.