The "Super-Flex" universal joint was not designed to be a "cure all", but rather specifically to solve a binding problem that one may incur under situations such as full axle droop and spring wrap. Situations like a front drive shaft, where you have a lot of lift and have also installed buggy springs or revolver shackles in conjunction with your shackle reversal.

We have never made any secret of the fact that this joint does cause some vibration problems. (In fact we will not even sell it unless the customer is aware of its limitations). This is due to the introduction of the 3rd plane of operation, which will cause the drive shaft to run eccentric. The amount of eccentricity is a function of how steep the drive shaft runs to begin with.

Through a zero degree angle there is no eccentricity and as the angle increases the amount of eccentricity will increase. The amount of vibration you will experience will be factors of the angle and the weight of the drive shaft. In theory if your drive shaft weighed nothing there would be no vibration forces as a result of running the drive shaft running eccentric.

As a simple test, we've installed these universal joints in the rear drive shaft for our (pretty much stock) Grand Cherokee. Admittedly the universal joint angles are minimal (less than 3 degrees), We fully expected that at some point, we would find the vibrations to be unacceptable our amazement we didn't experience anything annoying until we reached a speed of about 72-73 MPH. I believe this would be about 2300 RPM on the drive shaft. This drive shaft was also about 2X heavier than stock as it was one we made with a 2" X .120" wall tube.

Of course if you do not have good drive shaft geometry your drive shaft it will vibrate anyway. This would be a torsional vibration or the building and releasing of torque 2 times per revolution on the drive shaft. These types of vibrations may have a tendency to feel less severe than a radial vibration or imbalance. However we believe that they are actually harder on the attaching gears than the radial vibrations (assuming speed isn't excessive) this is because these torsional forces cannot be controlled by the speed of the vehicle and effectively occur 2 times per revolution of the drive shaft regardless of the vehicle speed and their strengths can only be controlled by load of the vehicle. Under normal load situations the net forces resulting from the torsional loads would actually be greater than the radial forces of a slow spinning shaft with the "Super-Flex" universal joint.

Again the "Super-Flex" universal joint is not claimed to be a "cure all". Ultimately to utilize the greatest flexibility of your suspension and have the smoothest drive shaft possible, our recommendation would be to:
 

1. Install a custom high pinion differential with the pinion positioned properly for a CV drive shaft.
2. Utilize a CV drive shaft with the grinding and machining necessary for maximum flexibility.
3. Use a Toyota slip yoke, spline stub and flange at the differential end.
   3a. The Toyota joint assembly would allow for a little more than 40 degrees prior to binding. It is however our opinion that using the Toyota joint assembly would be a compromise in strength as the Toyota joint is smaller than the stock 1310 series, the size and location of the grease fitting and the substantially thinner central body.

Alternatively, if this is not the kind of money and effort you want to spend and the drive shaft is not going to be turning at high speeds (locking hubs or other disconnect), I think the "Super-flex" universal joint is a very good solution. Certainly it is the simplest and most cost effective solution to a binding drive shaft problem in many situations.

If we can answer any more questions or you would like to place an order for
any of these options, Please feel free to call.