Perfectly normal. Only a handful of vehicles produced have equal axle widths front to rear. One of the reasoning is it keeps the rear tire tracking closer to the front tire in a turn.
What exactly does normal mean? Normal for a Bronco, or normal for a 4x4, or normal for a subgroup that doesn't represent the population?
Every Willys Jeep CJ built from 1942 to 1975 runs a 48.5 inch WMS. (Just one number for both ends.) The Willys pickup from the 40's to the 60's run a 59.25 up front, and a 65.5 out back. So 5+ inches wider in the rear. The 87+ Chevy K trucks are 71 up front and 67 in the rear. Every Dually I've ever seen is pretty wide out back.
It's all about packaging, and steering. If you want higher steering angles, you need a wider front axle. If you want rear tires that fit under the wheelhouse, you need a narrow rear axle. That's why the Bronco is narrow out back. So
@nvrstuk and
@Yeller are right again. Normal. (nothing I like less than applying statistics to non Gaussian multi-modal distributions. Please forgive this Six Sigma Black Belt...)
As far as the big bearing vs small bearing, the answer to
@joeray is "no." And "yes." Assuming that spline engagement is constant...Sometimes BB is wider than SB. Sometimes not.
@Viperwolf1 posted this back in 2009. It's still true. And they are all within 1/4 inch.
'66-'75, 28 spline, big bearing
short side: 26 15/16"
long side: 29 1/4"
'66-'75 28 spline, small bearing
short side: 27 1/8"
long side: 29 5/8"
'74-'75 28 spline, big bearing/small brakes
short side: 27 1/4"
long side: 29 3/4"
'76- '77 28 spline, big bearing/big brakes
short side: 27 3/16"
long side: 29 11/16"
