Minor rear vibration.......

I traced that kindof thing to my rear pinion angle.
>My rear springs are pretty soft, And I have fair bit of power. This is a bad combination.I cannot nor do I want to, run a snubber; the rear end is just too low. I run it there to suit my driving style which is stuffing it into corners,sometimes too hot. And the cops don't bother me about altered ride height.
>When I apply the power, the pinion wraps up quite far, so I have to have a fair amount of nose down in compensation, so that when the power is transferring from the driveshaft to the pinion,it is doing so at a good angle. Well all that nose down causes a vibration when running easy. I have gotten used to it.
> A high pinion angle causes the U-joint cups to oscillate forward and backwards during operation.I call it dancing. This dancing cannot be compensated for in the balance.
>To see this, the next time you have the rear tires off the ground, with the jack under the pumpkin, get eyes on a cup that is anchored in the driveshaft, then with the tranny in neutral, rotate a rear tire and watch that cup.When the cup is at the top it is in the rearmost position, and when it is at the bottom, then it is in the frontmost position. I think it can oscillate about a quarter-inch or more, depending on the set-up. Next reposition and jack the body up,to let the rear suspension droop. Now check the extent of the oscillation again. Notice how, with the increased pinion angle, now the oscillation is greater. Any oscillation here could in theory be compensated for by an equal oscillation at the front. Could be,in theory.But it would require an oscillation equal in degree, but opposite in direction, and in the chassis, that is just not doable. So then a certain amount of oscillation is unavoidable. The usual cure in stock vehicles is to set the pinion angle in the middle some where with respect to how the vehicle is intended to be driven.
Along we come and double the engines power and alter the ride-height, and all-chaos breaks loose back there.lol. All we can do is minimize the dance with respect to power transmission, and axle wrap-up, and the rest we have to live with.
>I can't say that this is your problem, but it is worth checking out.