| Sirrotica |
01-12-2023 11:01 PM |
The reason the later cars had boxed lower arms is mostly because they had a rear sway bar. The sway the bar is fastened on would squeeze the lower arms together when the bolts were torqued, and would flex as the bar was working. The only way to use unboxed arms with a sway bar would be a completely different bar, and mounting system, or use spacers inside of the lower arms.
I've been under a heckuva lot of GM 64-72 GM A/G bodies, and I've never seen any boxed upper arms on any of them.
The early cars tended to rip the crossmember out where the upper control arms mounted, especially on stick cars. GM then made the braces that connected to upper pivot bolts to the lower pivot bolts to tie, and triangulate the crossmembers strengthening the whole rear suspension mounting system. I saw plenty of the early cars rip the upper crossmember out, I never saw the ones with the brace system installed rip out though.
Jacking the rear of the cars up really increased the wheel hop problem as it threw the geometry way off, just lowering the rear, would completely get rid of the problem in most cases. Air shocks also screwed the geometry up as they were trying to twist the rear axle upwards in the front because the shock mounts were behind the axle centerline, throwing the pinion angle off. Just the opposite of the way the pinion angle should be for optimum traction.
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