Mod­ern­iz­ing the Buick Driv­e­line

Ditch­ing the Dy­naflow slush­box and torque tube for con­tem­po­rary cruis­ing com­fort

Street Rodder - - Contents - By Barry Kluczyk Pho­tog­ra­phy by the Au­thor

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.

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