I just installed a fuddle 3800 in my car and had trans built. I have never had a car with stall in it before and am not sure if this one is working properly or if something is wrong. When the converter locks up it get a horrible vibration depending on what rpm it goes into lock up. If i am coasting down the road when it locks up it dose it smoothly, but if i am on the trottle say rpms are about 3000 it vibrates the hole car when it locks up. It also acts fine at WOT.One other thing i noticed is that the car kinda pulsates back and forth if just coasting or at a low rpm when locked up. Has anyone experienced this. By the way the car is in desperate need of a good tune, but not sure if that would have any affect.

 

not sure what the problem is but that is not normal, mine locks up the same at any rpm

 

Depending upon how exactly your vibration feels, I would get underneath again and check to make sure your converter bolts are good and tight against the flywheel. Also, while you are under there double check your bell housing bolts. Excessive vibration is not a good thing.