HI SPENCER , NO ON THE PINION ANGLE , WHEN YOU GET ON THE THROTTLE THE TORQUE OF THE ENG CAUSES THE PINION TO TURN UPWARD AND IF THE SPRING BUSHINGS ARE WORN OUT IT CAN LET THE DIFF TWIST TOO HIGH , AND IT MAY BE IN FACT GOING TO HIGH , PAST THE NORMALL ANGLE , WHAT HAPPENS WHEN YOU PUT THE WEIGHT IN THE BACK , THE BACK END SQUATE DOWN AND THE PINION TURNS UP AFTER REPALCING THE BUSHING , IF IT STILL VIBRATES , THEN GET A 2 DEGREE SHIM AND PUT IT IN THE BACK SIDE OF THE SPRING PAD AND THAT WILL TIP THE NOSE DOWN, TRY IT AND SEE IF IT DOESN,T HELP , THEN UNDER TORQUE IT WILL TEND TO TURN UP TO ANORMAL DRIVING ANGLE ,,ANYBODY EVER DONE ANY DRAG RACING WITH CHRYSLER CARS , THEY USED TO OFFER A BIG RUBBER SNUBBER TO BOLT ON TOP OF THE REAR AXLE RIGHT ABOUVE THE PINION SO WHEN IT TURNED UP ON ACCELERATIION IT WOULD BUMP THE FRAME AND STOP THE PINION FROM CHANGING ANGLES AND BREAKING U JOINTS , AS FOR THE DOUBLE CARDAN JOINTS I WOULD THINK ANY GOOD DRIVE LINE SHOP COULD MAKE ONE , FACT IS NISSAN DOES HAVE ONE IN THEIR PICKUP, FOR THOSE WHO ARE NO FAMILIER WITH THE TERM IT IS 2 U JOINTS AT ONE END OF THE DRIVE SHAFT IN A COMMON CARRIER BUT THE 2 JOINTS ARE CONNECTED BY A SMALL MOVABLE ARM IN THE MIDDLE OF THE JOINTS AS ONE JOINT TURNS ONE WAY THE OTHER CAN TURN THE OPPOSITE WAY THERE BY CANCELLING A DRIVLEINE VIB AND CAN TAKE EXTREM ANGLES, ROD GORRELL I BELIEVE HAS HAD ONE DONE ON HIS RODEO SOME PLACE AROUND WINSTON SALEM N.C., THEY MAY BE CALLED C.V. JOINTS NOW DON,T KNOW FOR A FACT THOUGH , BUT THEY HAVE BEEN USED IN LINCLON S CADDY AND IMPERIALS FOR YEARS .. JERRY