The jumpy, restless editing betrays Sam Peckinpah's inability to concentrate on the exposition of "Convoy," a wayward rabble-rouser about indomitable truckers now at area theaters. To put it bluntly, "Convoy" is the sort of script even Peter Fonda might reject.

Through some unfortunate chain of circumstances it has ended up as a cinematic ball-and chain reuniting Peckinpah with Ali McGraw, who made her last appearance five years ago in "The Getaway," and with a trio of actors who played key roles for him in other films - Kris Kristofferson, Burg Young and Ernest Borgnine. These troupers may wish they'd made a getaway before signing on for a "Convoy," which suggests a shotgun misalliance of "Billy Jack" and "Smokey and the Bandit."

Nominally inspired by a hit Country and Western ballad now three years old, "Convoy" trumphs up a story of three amible truckers - Kristofferson, Young and Franklin Ajaye - forced into revolt by a corrupt, sadistic highway patrolman. Borgnine plays the disreputable officer of the law in vintage Fatso Judson-style as long as it appears to serve the purposes of the story. Unfortunately, this is a story that can't make up its wee bit of mind. It vacillates between outraged, self-righteous melodrama and rowdy, countrified facetiousness. When the latter frequency is switched on, Borgnine modulates from sadist to stooge and recalls the Jackie Gleason character in "Smokey."

Cast as a passing photo-journalist (inspired by Candice Bergen?) who ends up riding shotgun with Kristofferson, McGraw never quite fits into the picture. Five years in retirement haven't increased her expressive range, which remains bounded by a smirk and a frown.

Although MacGraw and Kristofferson appear to have sinewy physiques in common, they don't arouse ardor, or even idle amusement, as a romantic team. The ads that show MacGraw standing behind Kristofferson and embracing his bare chest look like a burlesque of the Kristofferson-Streisand pose for "A Star Is Born," in which Streisand was in front and the apparent aggressor too. MacGraw's backseat status turns out to be exaggerated in the movie itself, where her character is invariably depicted retreating to the sleeping alcove of Kristofferson's rig when the road ahead calls for top speed and defiance of all roadblocks.

While one may understand Peckinpah's impulse to skip over it, the lack of a credible exposition undermines the whole movie. During the first extended conversation between hero and heroine, the director loses interest almost immediately and begins seeking pictorial nourishment from shots of the truck rolling along the highway. This tendency becomes habitual.

Unable to transcend the limitations of his material on this occasion, Peckinpah overcompensates on the slightest provocation, using the vehicles to kick up a picturespue dust storm on the Alamogordo desert that probably drove his cameramen frantic and devising a violent showdown that has no dramatic justification but confirms his flair for visually complicated and dynamic scherzos.

There's even a demolition production number in which the trucks, ostensibly manned by the good guys, go on a mechanical-monster rampage. This sequence, in which the trucks become oddly reminiscent of Rodan, Godzilla & Co., may explain the movie's evident popularity in Japan.

In distincitive oddities like "Bring Me the Head of Alfredo Garcia" and "The Killer Elite," Peckinpah contrived to impose enough of his own kinetic excitement and turbulent, sardonic feelings on tawdry and pedestrian stories, to lift them out of wellworn ruts. In "Convoy" the best he can do is to pretend he's getting somewhere by noisily spinning his wheels. More often than not even his visual pyrotechnics fall short, and he's left trying to rationalize nonsenscial characters and conflicts by imposing his sentimentalities about men of war on them.

Peckinpah is a filmmaking heavyweight, but in "Convoy" all he's doing is fighting off the boredom and frustration that grow out of coping with stupid material.