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Why is the battery terminal bolt different for positive & negative

The bolt that clamps down the contact for the negative terminal is 10mm; the bolt on the positive is 11mm. Why? '87 Toyota pickup Xtracab Delux long-bed, carbureted, 5-speed manual, red with white camper shell, green power crystals, platformate,and gl-7 (gets my teeth whiter.)

Are you positive both bolts are the factory original bolts? Maybe the threads on one of the terminal clamps got a little boogered and someone stuck an oversized bolt in there to take up the slack.

Or maybe a 10 mm bolt will not withstand the juice put out by those green power crystals… Red power crystals, 10 mm might work. Green needs 11 mm.

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If they’re top-mounted terminals, I’m betting the previous owner replaced one of the battery cables.

If they’re side-mounted terminals, maybe it’s to make sure you don’t hook up the terminals backwards.

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Someone may have replaced the metric bolt with a 1/4" bolt, that would have a 7/16" head which is close to 11 mm.

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That would be my guess. Just as an aide the bolts are 6mm the nuts should take a 10mm wrench on most Toyota’s.