4sp vers auto shaft length

wish4hemi said

The 4 speed shaft is longer, but the slip yoke for a 727 and a post-'66 833 is the same (30 spline). The 904 and pre-'66 833's use 26 spline slip yokes. U-joints could be 7260 (small, 2 1/8") or 7290 (big, 2 5/8"). http://www.brewersperformance.com/history.htm

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This is correct,

The 727 and a-833 share the same yoke but not the drive shaft.

The 904 and a-833 share the same drive shaft but not the yoke.

There are a few different size u-joints and most 904's have the smaller u-joint but is fine for mild builds, those with bigger horsepower will or should have a custom shaft built anyway so the u-joint shouldn't be an issue.

Most pre 66 a-833's (all a-bodies, some mid size and trucks) are ball and trunnion u-joints so they don't have a slip yoke.