Modernizing the Buick Driveline
Ditching the Dynaflow slushbox and torque tube for contemporary cruising comfort
Although Oldsmobile claimed bragging rights to the first practical automatic transmission, with the '40 availability of the Hydramatic, Buick’s two-speed Dynaflow transmission, introduced in 1947, was the first to incorporate a torque converter as the fluid coupling used to transfer engine power.
The advantage of a torque converter, which would become the industry norm, was that its stator enabled the engine’s power to be multiplied for greater off-the-line acceleration. The four-speed Hydramatic’s coupling was a torus, which didn’t have a stator; and consequently, the transmission relied on an extra-steep 3.82:1 First gear to get the car moving.
Unfortunately, the Dynaflow’s torque multiplication capability didn’t translate well in real-world driving. Early models would get the vehicle launched in high gear, relying on the torque multiplication of the converter to enhance acceleration. But with, say, a '50 Roadmaster chiming in at a healthy 4,300 pounds and its Fireball 8 straighteight engine cranking out only about 150 hp, starting out in high gear made for glacially slooooowwwww acceleration, even if it was incredibly smooth. The transmission was revamped in 1953, updating it to only a single stator and a pair of turbines, but performance
improved only from painfully slothful to annoyingly sluggish.
That the Dynaflowequipped Buicks were criticized for their pokey performance in the ’50s should tell you all you need to know about how they stack up in today’s traffic. In short: They don’t—and that’s on city streets. You can forget about hitting the freeway, where every little old lady in her Kia is zipping along at 75 mph.
That was the conundrum facing David Weinberg and his '56 Buick Special, which couldn’t keep up with traffic despite its strong 322-cube Nailhead V-8. In almost any other car, a relatively straightforward swap to a modern overdrive transmission would do the trick, but it’s not so easy with vintage Buicks because along with the torpid Dynaflow there’s a torque tube between it and the rear axle. With it a ball-andsocket joint called a torque ball is used at one end of the torque tube to enable relative motion between the axle and transmission during suspension travel. The system allowed Buick to use soft rear coil springs instead of leaf springs for a smoother ride.
The problem is because the torque tube is effectively an element of the suspension, replacing it requires upgrading the suspension. That adds cost and complexity to the proposition, but with driveability of paramount importance, Weinberg decided to do a complete driveline upgrade and called on Brothers Custom Automotive to do the wrench turning.
For the project, Brothers located a freshly rebuilt GM 700-R4 transmission, while relying on a Heidts suspension, a Currie rearend, and Speedway to supply the axle and suspension components. They included a sturdy 9-inch rearend and a triangulated four-link rear suspension employing QA1 coilovers.
“It’s a serious, time-intensive project,” Brothers’ head honcho Bill Jagenow says. “Although all the parts to make it happen are available, it is by no means a bolt-in operation. Everything from the engine rearward changes and requires a good deal of fabrication, but the change in driveability makes it a very worthwhile endeavor for vintage Buick drivers.”
The Dynaflow was state of the art in its day, but so was snowy black-and-white television drawn in with rabbit ears. Times have changed and this Buick no longer has any trouble keeping up with them.
Because the torque tube is connected to the axle centersection and transmission, it’s logical to ask why the removable centersection from a later-’60s Buick with an open driveshaft couldn’t simply replace the torque tube version. Technically, it could. But because the torque tube was integral to supporting the suspension, a suspension upgrade would still be required.