Anyone who has studied GM over the years has witnessed scores of other market retreats. Names such as Euclid and Terex (both earthmoving vehicles), ElectroMotive (railway locomotives), Class 8 heavy-duty trucks, diesel-engine production (Detroit Diesel),  Frigidaire (home appliances), city buses and recreational vehicles long since have been shed. Big acquisitions such as Electronic Data Systems and Hughes Aircraft are a distant memory.

GM acquired EDS in 1984 for $2.5 billion and gained access to information technology, but it returned to independence in 1996 and was sold to Hewlett Packard in 2008. GM won a battle with Ford in acquiring Hughes in 1985 for $5.2 billion, chiefly for its electronics expertise. GM sold Hughes to Raytheon in 1997 for $9.5 billion that, compared with its purchase price, might have made the automaker a tidy profit.

Then consider Saturn, Chairman Roger B. Smith’s answer to fighting imports. Saturn lasted 20 years (1990-2010), although the plant GM built for its “different kind of car company” subsidiary in Spring Hill, TN, still makes GM vehicles. Gone, too, are Oldsmobile (closed 2004), Pontiac (closed 2010) and Hummer (closed 2010) plus a long list of short-lived nameplates.

And who can forget NUMMI (New United Motor Mfg. Inc.) the Toyota-GM joint venture to build small cars in GM’s Fremont, CA, plant? That lasted from 1984 to 2009, becoming a victim of GM’s bankruptcy. Tesla now makes electric vehicles in the Fremont plant that, ironically, compete with the Chevrolet Volt and Bolt EVs.

Most of GM’s sprawling parts-making divisions were folded into the Automotive Components Group in 1994 and transferred into the newly formed and independent Delphi the following year. In 1997 Hughes Electronics operations came under Delphi’s aegis, Delphi became a stand-alone business in 1999, underwent bankruptcy in 2005 and remains a major GM supplier.

Some might view these moves as a massive retrenchment, while others likely would argue it freed GM from managing and investing in operations not intrinsic to its core business of developing and assembling cars and trucks.

Opel historically has contributed technology and platform design and engineering for its U.S. parent, mainly Buick, including the current Buick Regal and the Cascada convertible. Saturn also turned to Opel for a series of Opel-developed models late in its lifetime, and Opel engineering played a key role in GM’s subcompacts introduced in the 1980s and the Cadillac Catera in the 1990s.

Cole, for one, concedes GM may lose some expertise as Opel departs, but the Detroit automaker still has plenty of engineering and product-development muscle.

“I think they are very well positioned now” without Opel, he says.

However, another WardsAuto source suggests Opel and GM likely will maintain “essential technical cooperation.”