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by Genghis




"I have a '77 Corvette with a 350 and the stock automatic. I also have a 400 motor from a mid-seventies truck. I'm planning on rebuilding the 400 as a powerful 406. I am wondering if I can use the stock Turbohydro 350 automatic if I have it rebuilt with beefier parts or will I need a better model transmission."

"Ryan, I can say that the stock transmission will be too weak to handle a stout 406, but it can definitely be beefed up to handle it. The question is one of cost vs. benefit. A small Turbo 350 has the advantages of lighter weight and lower parasitic drag when compared to the bigger TH400.....but the big tranny can handle a combination like you are contemplating in virtually stock form....."


I've loved the TH400 (Turbo-Hydramatic 400) automatic transmission, ever since Jim Hall shocked the racing world in using this beefy transmission in his revolutionary Chaparral racecar in the 1960s. Take a gander at the picture of this beautiful racecar I took at speed. It was amazing and historically significant. In truth, the Chaparral was a collaboration between Hall and clandestine efforts by Chevy engineers. General Motors had imposed a racing ban then, and the Chevy engineers' participation in the building of the Chaparral, was Chevy's backdoor, non-official gift to the racing world. One of Chevy's most significant contributions, was the use of their fantastically strong three speed TH400 automatic transmission. Not only was the mere usage of an automatic transmission in racing in the 1960s unheard of, but the superior performance of the winning Chaparral equipped with the TH400 automatic against the conventional manual transmissions of the day, was a rude awakening for the Chaparral's losing competitors that used four speed sticks. Not only could the Chaparral make faster and smoother shifts than the other racercars it beat, its TH400 automatic transmission was also stronger in construction and more durable under high horsepower stress than the manual transmissions it competed against.


6:32 AM: I'm in sitting in Mary, my 1972 Vette in her parking garage on Delancey Street in the Lower Beast Side of NYC. I give her gas pedal four pumps before turning the key, and with the turn of the key. Mary starts up....."Whir...whirr...whirrrr....WHUMP....WHUMP...WHUMP...WHUMP......" The exhaust note from Mary's small block Chevy mill reverberates against the cars around her, as she idles on choke. The walls formed by the sides, fronts and backs of cars around us, act as sounding boards to the strains of Chevy power.

Before she has a chance to settle down to a normal idle, I engage Mary's TH400 transmission, and we head out into the early morning darkness. We drive down Delancey Street under the hulking shadow of the Williamsburg Bridge until we get to the FDR Drive heading downtown. By the time I get onto the entrance ramp and I stomp of Mary's gas pedal eliciting a....."WAAAAAAAAAAAAAaaaaaaaaaa...." from her screaming motor, Mary's warm enough to be off choke as we blast past the ordinary traffic we leave in our wake. By the time we reach the Brooklyn Bridge, we're doin' 80 past the cars gettin' off for the bridge. We round the curve in that neat tunnel at the tip of Manhattan, and we maintain a steady fifty as Mary's BF Goodrich TA Radials strain at the limit of adhesion as we round the radius of the curve at the apex. We emerge from the tunnel on the west side and accelerate up to sixty on the West Side Highway heading uptown. I can feel Mary's TH400 trans eagerly welcoming each and every upshift as Mary's motor climbs in crescendos of revs.

We exit the highway at 72nd Street and drive east to Central Park, where we drive uptown along Central Park West, which is still light in traffic because of the early morning hour. At 81st Street near the Museum of Natural History, we cut into the park where a road runs through the park to the east side of Manhattan. At Fifth Avenue, we make a right turn. The light we encounter starts to turn, but before it does, we accelerate quickly to bypass the coming sequencing of sucessive red lights down the wide avenue. By the time we hit 50, all the lights ahead of Mary and me are GO GREEN! Amazingly, at the brisk pace we're traveling at between 45 and 50 with the motor running with a happy snarl, we don't hit even a single red light for four miles until we get back to Houston Street in the East Village.


I love having the TH400 automatic in Mary. I'm big on tradition as you all know, and to think that Mary's shares a common transmission with one of the most successful and and historically revolutionary racecars, is to feel a satisfaction that is difficult to convey to bikers who don't appreciate cars. I've never been a biker who eschews "cages" to the exclusion of them as part of the center of my motorvatin' life. I make no distinction. To me, my Harley 74 and my Vette share a place in my motoring heart. They are different, yet the same if ya know what I mean. Traditionally, I cherish the TH400 as much as Mabel's four speed transmission. Both can handle all the torque that any mill can generate. Why would any Shovelhead rider want to replace his great four speed trans, with an aftermerket tranny? The traditional four speed trans is so strong and durable, that it's the only transmission old big twin riders would ever need.

On a sidenote, I once had to ride Mabel the one hour ride to Andrew's Rosa's shop on Long Island, while her four-speed trans developed a leak. Within ten minutes of leaving the Lower East Side, Mabel's tranny was virtually empty. We made it to Andrew's shop in Huntington without any problems, and no damage to the transmission. Andrew said to me..."See Scott, this transmission is so strong it can run on oil fumes with no problems..." Andrew then rebuilt my trans and it's good as new.

Similarly, why would any Vette pilot wish to have any trans except the TH400? I've only owned two cars in my life. My first was a '64 Vette with the famous Muncie 4-speed stick. It too was great, but while I owned that Vette, I secretly wanted a Vette with the race-proven TH400 automatic---just as I yearned for a Shovel when I owned a Sportster. In my second car Mary, my '72 vette---I finally have the transmission that I coveted in the mid '60s.

I wish that I could make bikers who aren't into cars understand the satsifaction that a car can give, just as their Harleys fulfill their lives---but I can't. Like the biker saying from the old days goes....."If you have to ask you wouldn't understand." If you fall into the "hate cages" category, hey man---yer missin' half the fun in life. Let's just say that my Vette equipped with the righteous Turbo-Hydramatic 400 trans with its racing bloodlines, is an automatic success. Later.