The early-50's straight-8 Pontiacs were notorious for developing noisy pinion bearings in the rear end. The problem was caused by the lack of a ground strap from the frame to the engine, and starter current finding its way back to the battery by going down the driveshaft and springs to the braided ground strap from the body to the battery. Simply adding a heavy frame-to-engine ground strap solved the problem, but it could have been avoided by attaching the battery ground to the engine in the first place. Most body-grounded items like headlights, etc., do not draw enough current to require a battery cable sized ground wire.
Jerry
