gzig5 said

The issue with the aluminum case is the lower shaft is a loose fit in the case which allows the gears to move in relation to each other under high loads that wouldn't affect the steel case. The case can be modified with a bushing that tightens up the fit and gives the same performance as the steel cases.

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DionR said

To add to that, I think the aluminum case can wear at that lower shaft and further increase how much the gears moving away from each other. And when the gears deflect the result can be breaking teeth off.

In addition, AJ/FormS has said that there are fewer splines on the OD gear and that gear can easily be broken under a hard shift to "4th".

I've never broken one myself, but I've never had what anyone would call a powerhouse in front of one either. Always been too poor to do much more than a bottom dollar rebuild and add a cam.

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