The Porsche 934s were now eligible. Many of the top teams would field them, and they would sport Group 5 bodywork parts.
BMW entered a new 320 Turbo, which would be driven by David Hobbs.
The Chevrolet Monzas became much more hairy, and they were still the cars to beat.
The GTU class would see a season-long battle between Sam Posey in a Bob Sharp entered Datsun 260Z and Walt Maas in an outdated Porsche 914/6.
At Daytona, however, three Porsche 935s were entered, and Jacky Ickx and Jochen Mass drove the works car. The event was FIA listed, and those cars didn't run for points. They were defeated by a Porsche Carrera RSR driven by John Graves, Dave Helmick and Hurley Haywood. Bob Hindson, Frank Carney and Dick Davenport took the GTU honors in the BHR Porsche 911.
At Sebring, it was yet another Porsche Carrera RSR, driven by George Dyer and Brad Frisselle, who took the overall victory.The Jim Busby-Peter Gregg entry was the most valuable contender, but they ended up third after running on some debris on the track. Rainer Brezinka, Gary Hirsch and Fritz Hochreuter took the GTU vixtory in a Porsche 911.
At Road Atlanta, things would be quite different, with the Chevrolet Monzas now ready to fight. Al Holbert would win the race, but he had to wait until Carl Shafer's Chevrolet Camaro would falter. He finished second, with George Dyer and David Hobbs next.
Sam Posey, who drove the Bob Sharp Datsun 260Z for the first time, took the GTU victory, edging Bob Bergstrom in a Porsche 911.
The Laguna Seca saw a Porsche 934 take its first win, and the same could be told of Danny Ongais, who won his first major race. Walt Maas, in a Porsche 914/6, took the GTU win, beating Sam Posey in his Datsun.
At Mid America, Al Holbert was back to Victory Lane, as he dominated the event. Once again, his only opponent was Carl Shafer, who had to retire from the race. Walt Maas made it two in a row in GTU, and he won over Bob Bergstrom.
The Lime Rock race saw Al Holbert dominate a troubled field of cars. Hurley Haywood ended up second in Bob Hagestad's Porsche 934, while George Dyer took third in his Porsche Carrera RSR. Walt Maas again won the GTU class, but he was helped by the fact that Sam Posey lost two laps early in the race. The latter put up a fantastic race to finish 35s behind the Porsche.
The Mid Ohio race was won by David Hobbs, who ended up two seconds ahead of Al Holbert, who started from the back of the pack. A loose rear wheel forced him into the pits prior to the start. Sam Posey won the GTU class after battling all race long with Walt Maas.
Brainerd was a very interesting race, with five cars nose to tail for half the race. After a torrential rain occured, things changed a lot. Danny Ongais finally emerged from the rest of the pack, beating up Hurley Haywood. Walt Maas took a new GTU win in his Porsche 914/6, with Sam Posey right behind him.
The Paul Revere race was an attrition race, with George Dyer winning a race Hurley Haywood appeared sure to emerge as the winner. But the clutch let go. Sam Posey won the GTU class, just ahead of Dave White-David McClain in a Porsche 911.
The Hallett GTU race would be run under a severe heat. A three car battle took place for most of the race, with Walt Maas taking yet another win. Dave White finished second, while Sam Posey ended third.
It would be the first time GT and GTU cars would run separate races in IMSA history at Sears Point. David Hobbs garnered his second victory of the season. He was chased throughout the race by Al Holbert, who had to stop with a tire puncture. He finished second though, after a great race. The GTU race was a close battle between four cars, with Sam Posey, Dennis Aase, Walt Maas running nose to tail. Dennis Aase emerged as the winner when Sam Posey and Walt Maas had a coming together. They finished two and three.
At Pocono, Al Holbert was rated as the favorites, but he had to fight against Danny Ongais and David Hobbs. They both retired, and it left Al Holbert with a clear path to the chequered. Walt Maas and Sam Posey went on battling it over and the californian driver had his revenge, winning the GTU class.
The Mid Ohio race was a special event, featuring GTX cars, which would be eligible for the next season.
Three Porsche 935s were entered, and they ended up 1-2-3, with Peter Gregg coming up on top. He would not earn GT points, though. Hurley Haywood, co-driven by Bob Hagestad, did so in their Porsche 934.
Walt Maas easily won the GTU class when Sam Posey had to retire with a blown engine.
The fall Atlanta race went to David Hobbs, in his BMW 320 Tc, who ended up Al Holbert's winning streak. The latter finished second, and Hurley Haywood ended up third. The GTU cars had a race of their own, and it would be one of the closest finish in IMSA history, with Dennis Aase ending 0.015s ahead of Sam Posey.
David Hobbs won at the Laguna Seca race, and he and Al Holbert put on a big show, running together for most of the race. He would pass him close to the end but Al Holbert had clinched the championship. Walt Maas and Dennis Aase had a battle, with Sam Posey behind. Walt Maas won the race and also clinched the GTU Championship.
The Daytona Finale had a strong field, but the race was struck by many accidents. After a very wild race, Hurley Haywood wrapped up his third victory of the season, and the second place in the points standings. Kenper Miller finished second in the race with his BMW 3.0CSL. The GTU race was quite different, but neither Sam Posey nor Walt Maas would compete. Rusty Bond and Ren Tilton earned their only GTU victory of the season over Chiqui Soldevilla, both running in a Porsche 911.
The next season would see tremendous changes in the rules as GTX cars would be introduced. The Porsche 935s would become the cars to beat for years.