Back when General Motors was great, its different brands fought each other with animal ferocity.

Chevy tried to punch out Pontiac. Buick tried to break Oldsmobile’s back. Cadillac stomped on any moves Buick and Olds made onto its turf. It was a back alley brawl that honed the competitive edge GM needed to dominate the U.S. market.

But in the quest for efficiency, corporate types began to trim away the divisions’ autonomy and impose a centralized structure. This is when, in the late 1960s, GM’s decades-long slide actually began.

It started with GMAD, the corporate Assembly Division that built different brand cars in the same plants. Why have overlapping efforts, the thinking went, when the corporation can eliminate redundancies and cut costs?

In the 1970s, that kind of rationale made it acceptable to put Chevrolet V-8s in Oldsmobiles. Buyers who thought they were getting something special – namely an Olds Rocket V-8 – felt cheated when they found a Chevy engine under the hood, much to the bewilderment of the corporate cost cutters.

A decade later, this same rationale forced the divisions to share expensive body-side aperture dies. That led to the much-criticized cookie-cutter designs of the 1980s.

And so it goes, even to this day.

Last year, the auto maker began putting GM badges on the front fenders of every vehicle it makes in the U.S. market.

“Gee, I didn’t know Cadillac was made by GM,” said a yuppie Gen X-er I know. But thanks to those badges, she now is aware the corporation that is padlocking plants, laying off thousands and teetering on the brink of bankruptcy makes Cadillacs.

Just a few months ago, the auto maker launched its Red Tag sale in a desperate attempt to get customers into showrooms. But it was launched as a GM Red Tag sale! Have you ever been to a GM dealership? No, of course not. They don’t exist.

Maybe that was a turning point. The company quickly dumped the GM campaign and let the brands advertise their own product-specific Red Tag prices.

Now comes word that GM’s field-sales staff is being realigned to work with specific brands, rather than be corporate reps to whatever dealers are in their region. Good move!

GM’s glory days were when it was just a holding company, and the divisions were freewheeling car companies. There was a chance in the early 1980s to revive that model. Today it’s too late.

Even so, the less GM tries to “corporatize” its brands, the more it celebrates their diversity. The more autonomy they get, the faster GM can start clawing its way back.

John McElroy is editorial director of Blue Sky Productions and producer of “Autoline Detroit” for WTVS-Channel 56, Detroit and Speed Channel.