Just before I installed my v/b, my trans developed a wierd 3rd to 4th shift flare. If I am light to moderate on the pedal, it up shifts then downshifts once really quick around 80kph then shifts into 4th normal. Since I put the v/b, it seems to be magnified.....any ideas....the trans is stock and I am running her on smarty #4 and 3x3 on the edge. If she is at the floor...I do not notice it.

tia

the Tree

 

When the tranny shifts into OD it unlocks the converter for a split second, shifts into OD, and then relocks the converter. Is that what your feeling? Also, it's quite possible that your torque converter lockup clutch is slipping.