Yeah. I saw that in a YouTube vid the other day. I think it's the Tremec app. It basically turns your phone into an angle cube. Maybe it tells you where to stick it, too! lolI have been " told" that there is an app you can download to your phone??
Let’s say the engine/trans is angled downward at three degrees and the pinion is angled upward two degrees. If we were to extend the operating angles of the engine/trans and the pinion, you can see that these lines will be within one degree of parallel. This arrangement is very close to an ideal overall driveline operating angle because the two angles are within one degree of parallel.
Now, let’s change the pinion so that its operating angle is two degrees downward. The extended line from the pinion angle will now intersect the engine/trans angle, creating an intersecting overall operating angle that generates the vibration you’re experiencing.
So the solution is to change the overall operating angle.
There are two ways to do this: One is simple. The other is far more difficult.
The difficult way: If we decide to leave the pinion operating angle at two degrees nose-down, the engine/trans angle would need to be raised to a minimum of a one-degree tail-up attitude. And this will probably be difficult since that TKO trans is already somewhat tight to the floor pan. We’ll assume you currently have the typical tail-down angle. Placing a ½- or ¾-inch shim between the trans mount and the crossmember will help, but probably not enough. In our experience, it may take 1½ to two inches of spacers to move the trans angle more than a degree.
The simple way: The second option is to change the pinion angle. Frankly, this is far easier.
With adjustable upper control arms, this gives you the ability to lengthen the upper arm which will raise the pinion angle from a nose-down to a more appropriate nose-up angle. Again using our original three-degree engine/trans tail-down angle, adjusting the pinion to a two-degree nose-up angle will put the overall driveshaft operating angle within one degree of being parallel.
According to a post I found from Pat Casey, at UPR sales many years ago, the stock upper is supposedly 9 3/8 inches. I assume that fixed arms are stock replacement, and therefore the same length, but I cannot find the actual dimensions on BBK's website (manufacturer of Gripp, it seems).I would check the length of the upper control arms compared to stock stuff.
I have a pair of uppers (new) on a shelf I could measure.
Many drag racers adjust their pinion angle to optimize operating angles for maximum power delivery when the car is under power. The less operating angle in the u-joint, the more power will make it to the rear tires. By compensating for pinion rise in their static pinion angle, racers can minimize pinion angle during hard acceleration. Ladder-Bar and 4-link style suspensions offer a lot more control of the axle, and therefore the pinion. But drag racers will still set up the pinion angle to compensate for the rise. According to Pro Stock chassis builder, Jerry Bickel, ladderbars require ½° of pinion angle. A 4 link requires 1-2½°. Vehicles with leaf springs can require 6-7°.