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Originally Posted by MattG
It should be OK to drive, just take it easy on the shift lever, don't force it if it doesn't want to go in easy. As Stan said, it does appear to be a fatigue issue. However, fatigue is dependent on the stress - the greater the stress, the fewer the cycles before it breaks. Keep the stress below some certain level, and it'll never break.
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The early hex design is loaded with stress risers. All of the breaks I have observed on them initiated on the surface, right at one of the corners of the hex. Combine this with the poor surface finish, plating, nearby bend to the right (and tooling marks from the bending), iffy-variable weld (brittle metal + cross section reduction), near total rigidity of the lower part of the lever compared to the upper, etc and it's easy to see why the thing has to fail where and how it does. The part sees fully reversed cyclical loading of variable amounts which tends to be worst case..worse than cycles at identical loading or in just one direction for example. And it is all concentrated right at the weakest part of the shaft as installed.
The new lever with it's better surface finish, round cross-section (spreads the stress out), better alloy, and larger diameter should be basically bulletproof by comparison. An added benefit is that it's greater weight improves the nature of the shift, subjectively. Same concept as a heavier shift knob.