Grade: D-

If Michael Bay had decided to call this half-sequel, half-reboot of his Hasbro toy franchise “Transfourmers,” the title would have been the wittiest thing in the movie, an elephantine stinker that’s the very definition of sound and fury that signifies nothing. But instead we just get a subtitle that makes you wish the bloated, puerile sludge-heap of mindless mayhem, sub-sitcom humor and chaotic plotting would go over the edge, already, and meet a well-deserved demise.

The script, credited—if that’s the proper word—solely to Ehren Kruger, who was co-writer on parts two and three, is set five years after the “battle of Chicago” that reduced much of that city to rubble last time around. (Amazingly, all the landmark buildings have been miraculously restored to their former glory in order to be wrecked again.) After a prologue that shows that the devastation of earth that killed off the dinosaurs was the result not of an asteroid collision but an attack by the transformers’ creators (a notion that will set up the emergence of what are called “legendary warriors” in the final reel—presumably aficionados of the toys will understand this), focus switches to our new human hero. He’s Cade Yeager (Mark Wahlberg, replacing Shia LaBeouf), a self-styled rural Texas inventor/robotics engineer who finds a half-wrecked old truck cab while plowing through the debris in a long-shuttered theatre and, taking it back to his barn for work, discovers it’s actually old Optimus Prime (voiced by Peter Cullen), whom he brings back to mechanical life.

That sets off alarms with sinister CIA black-ops specialist Harold Attinger (Kelsey Grammer), who’s been waging a secret war to wipe out all remaining Autobots—and is willing to trample on citizens’ civil rights, even that to life, in doing so—while seeking to feather his own nest prior to retirement. He’s in league with the Autobots’ new nemesis, a Decepticon bounty hunter called Lockdown (Mark Ryan), to whom he’s pledged to turn over Optimus in return for a “seed,” which will serve as the source of the mind-malleable element humans have none too imaginatively dubbed transformium, the source of the transformers’ power to—well, transform. Attinger will turn over the seed to his other colleague in malfeasance, Joshua Joyce (Stanley Tucci), the head of KSI Industries, who will employ the material to assemble an army of earth-controlled transformers to serve as a defense against alien invaders (as making lots of moolah off its other potential uses). The prototype, Galvatron (Frank Welker), is already operational, cobbled together from bits and pieces of the defeated Megatron—not a good sign if one’s seen all the Frankenstein movies in which the monster is ruined by having the brain of a killer implanted in it.

Anyway, Attinger sends his henchman Savoy (Titus Welliver) to retrieve Optimus, which he attempts via heavy-handed threats to Yeager, his nubile seventeen-year old daughter Tessa (Nicola Peltz) and his doofus, surf-obsessed partner Lucas (T.J. Miller). They escape, due to the intervention of Tessa’s secret boyfriend Shane (Jack Reynor), who just happens to be a race-car driver, but in doing so become as big a target for Attinger and his minions as Optimus and the surviving Autobots he calls out of hiding—Ratchet (Robert Foxworth), Hound (John Goodman), Drift (Ken Watanabe), Crosshairs (John DiMaggio), and the voiceless Bumblebee—to make up a dirty half-dozen. (Later little Brains, voiced by Reno Wilson, will be freed from Joyce’s lab to join the group.)

It would take laborious effort to disentangle the narrative chaos of the rest of the movie. Suffice it to say that it first involves humans and Autobots staging a raid on Joyce’s stateside building in Chicago, which leads to much over-the-top action, to a battle inside and outside Lockdown’s massive spaceship, with humans dangling from cords attached to the old Sears Tower, to a final showdown in Hong Kong, where Joyce, realizing the error of his ways, has joined forces with the Yeagers against Attinger and Savoy while Optimus and his fellow Autobots—with the aid of those legendary warriors, which can transform into mechanical dinosaurs—take on Galvatron, Lockdown and their myriad bots. Frankly it’s difficult to tell what’s happening and why for much of the running-time, but it doesn’t really matter, because it’s all just an excuse for a constant stream of CGI set-pieces filled with frantic chases, innumerable hair’s-breadth escapes, gargantuan-scaled fights, massive explosions and endless collapsing buildings, all delivered with in-your face 3D effects by cinematographer Amir Mokri (debuting the new Imax digital 3D camera) and ear-pulverizing audio, the latter courtesy not only of Steve Jablonsky’s bellowing score but Peter J. Devlin’s Dolby Atmos/Datasat ratcheted-up sound design.

The latter, unfortunately, also allows one to hear the painful dialogue, not only the stentorian pronouncements by Optimus, Galvatron and Lockdown and the unfunny banter of the other Autobots (with Goodman’s Hound especially irritating) but the snarling banalities delivered by Grammer and Welliver, as well as the pompous directives—and later screaming hysterics—assigned to Tucci’s master-of-the-universe-turned-cowardly–good-guy Joyce.

Worst of all, however, is the juvenile badinage among the other human characters. All that Kruger has been able to think of to give Wahlberg’s hero any character is to have him be an obsessively protective dad, which sets up a stream of supposedly humorous zingers between him and Shane (whom he calls “Lucky Charms”) that are beneath the standards of any respectable sitcom writer. Reynor’s responses are equally vapid. As for Peltz, she’s given little to say apart from damsel-in-distress banalities. But talk isn’t her major function: wearing short-shorts that would have made Daisy Duke blush, she’s there merely to provide eye-candy for the drooling adolescent boys who represent a big chunk of Bay’s target audience—in other words, she’s the new Megan Fox. Happily, one has to endure the witless surfer-dude ramblings of Miller’s Lucas relatively briefly. His abrupt disappearance is meant to be a crushing blow, but given how annoying the character is (not the talented Miller’s fault), what happens to him is more likely to cause relief rather than regret.

Obviously in such circumstances acting is a secondary concern, but it must be said that Wahlberg, as usual, handles the physical demands of his part well. Grammer and Welliver are terrible in every sense, and there’s an especially bad turn by Thomas Lennon as a nervous White House Chief of Staff, which doesn’t bode well for the new “Odd Couple” series in which he’ll play Felix Unger against Matthew Perry’s Oscar Madison. Coming off best is Tucci, simply because he’s one of those actors one can admire for trying even when he’s mired in complete schlock.

One can appreciate “Transformers: Age of Extinction,” as far as that’s possible, for doing in spades what Michael Bay does best: blowing things up real good and filling the screen with endless, overwrought action, enhanced in this instance by the Imax 3D format (used with absolute abandon, since subtlety in any respect is not part of Bay’s vocabulary), and ear-splitting sound system. (The picture is scheduled for release in 2D and regular 3D as well, though it would be a shame to forgo the really big screen option in this instance, since the visual and aural overkill—which extends to the brutal 165-minute running-time—is really all the movie has going for it.) You also have to give the project some back-handed credit for realizing that a big portion in gross potential will come from the Asian market and deciding to pander to that audience by setting the final confrontation in China, where viewers will probably leap at the chance to see their locales smashed to smithereens as much as U.S. ones enjoyed watching the White House blown up in “Independence Day”—a sad commentary on the mentality of today’s worldwide moviegoers.

Except for those who desire for some reason to immerse themselves in such brainless bombast, or fans who, whatever their chronological age, still play with the dolls that inspired the series (or remember them with nostalgia), it’s hard to imagine that anybody will glean much enjoyment from this fourth installment in a franchise that should have been relegated to the scrap heap long ago but, given the realities of today’s Hollywood, will probably go rumbling on indefinitely, raking in billions. Go figure.