There is a small percentage of folks that experience vibes after a re-gear. Each case I've read is slightly different than the next, so it's hard to pinpoint a common issue. My vibe issue might be unique in that I've been chasing it for a long time, thrown a lot of parts and experiments at it, and have made improvements, but still no total resolution. There has been discussions where resonant frequencies are introduced as a result of the gear change and drive shafts spinning faster, ujoint critical operating angles, and the like. If you can, try to pinpoint which drive shaft might be creating the vibe. Try pulling the front on first. Many folks with the 42rle auto trany find pulling the front shaft cured the vibes, some it did not.