isnt the vib felt more with it on than off, since the vibs are kind of directed more towards the driver, instead of just reverberating against itself, but it is safer to have it on, even if it is felt more? its the anti harmonic dampener for the driveshaft... i think the crucial point with stock 3.08's is around 80-90 mph and with 4.10's it happens at a much much lower speed like high 50's or 60's maybe... i cant remember which speed exactly. also, an aluminim driveshaft will flex more to harmonics than a steel one... just my .02 that i picked up somewhere, im just too scared to take her off...