This part was developed and tested for a 1969 IRS drag racing sedan that runs in the high elevens at the drag strip. Needless to say the CV joint flange (spider gear) often broke. At the start it did not break parts but as years went by, the car got faster, and more, and more parts broke. One year the car was taken to the track four times and couldn't even make one run as the CV joints or spider gears kept breaking. After the "Washington Anti Shocker" (�) was installed, it didn't break any parts for four years, even after hundreds of runs. It works on swingaxle or IRS, vehicles alike. However, it requires the 1967 and later straight clutch arm on the transaxle and that our copyrighted instructions are followed.