I replaced the rear springs with the XHD mopar springs for two reasons. One, I thought the butt end looked low (and it was by measurements), and after having a shop replace my ball joints and tie rod ends, the car had taken a significant list to the port (left) side. I felt like I was on an Italian Cruise ship. In all seriousness, there was about an inch or more difference between the measurements from the rocker panel (front and back) and the opposite side. I had to back out the adjuster on right side all most an inch or more compared to the left side to get it to side near level, and there was still a 1/4" or more difference between the two sides.
I got some great info by searching the CC.com site, and found this thread particularly instructive:
http://www.cuda-challenger.com/cc/index.php?topic=79623.0So I checked the installation of the bars and they were installed on the correct sides; I had the 779L on the left and the 778R on the right. As a mechanical engineer, I understand the idea behind torsion springs, and material properties such as the elastic region, and the permanent set that may occur if a material yields.
My first check, once I pulled the bars out was to lay them on the floor side by side, and I noticed they didn't line up perfectly. With the hex on one end of the 778R flat on the floor, the opposite end is 90 deg (so there's a 30 deg offset from one end to the other), and it was pretty darn close since I used a square to measure it. With the hex on one end of the 779L flat on the floor, the opposite end was out of square by .075" across the flat. The flats are 1", and with a .075" gap, and some trigonometry, I come up with between 4 and 5 degrees of offset. Furthermore, the lower control arm is 13", and some additional trigonometry gives me the 1" offset that I am seeing.
Here are my questions:
1) Is this 5 degree offset the reason for the left and right torsion bars? Is this to account for drive train torque?
2) Is the left and right part number designation intended to ensure that they get put back in the same way due to material property concerns?
Thanks
Rick