severe vibration-need help
 

I finally installed the 1996 legacy 4eat with converted #2 speed sensor, converted rear(put 96 rear gear on original limited slip gear set). the speedometer reads correctly and I do not have error codes.
The transmission does not seem to perform right. I am trying to figure out what is not working exactly but here is what I have founfd so far

Terrible vibration at 35-40 mph especially when power is applied- not coasting

shifting from D to 3, there is no difference- seems like overdrive is not engaged

I seem to remember car would free wheel if power was off- does not feel the same
on a slight hill car does not roll back ward at idle


I am looking for help in isolating these issues- I do not want to give up on the automatic

Thanks for help

I tested today and found out that the vibration- very loud drumming, is right at 42 mph- louder with slight power on quiter if neutral pwer- does not mater in 3rd OD or neutral. Nor other speeds up to 70 mph had a peak in vibration. Any thoughts???

How are all the joints on the driveshaft?

They were stiff but moveable. What level of movement typically causes vibration-for example the joint falls down under it's own weight etc?
Also, if drive shaft and flanges were marked for orientation, how were they marked from factory?
Thanks

drive vibration problem solved
 

I changed three things
put in fourth drive flange bolt that I forgot to install
put pb then oil in the slightly stiff u joint
matched paint marks on driveshaft and rear flange

vibration at 43 mph gone- quiet and smooth thruout.
Not sure which of the above fixed problem but it is a dramatic improvement.