Thursday Trivia

Thirsday Trivia
Welcome to Thursday Trivia where we offer up a historical automotive trivia question and you try and solve it before seeing the answer after the jump. It’s like a history test, with cars!
This week’s question: What was the first car company to popularize the limited slip differential on a production car?
If you think you know the answer, make the jump and see if you’re right.
Most enthusiasts prefer cars that are front or mid engine, and rear-wheel drive. That’s because oversteer is vastly more fun to manage, and more effective for maintaining speed, than understeer.
Limited_slip_diff_coneTo be effective at even modest street driving a rear axle needs a differential. This is because when turning, each of the rear wheels describes a different arc, one smaller than the other and hence necessitating a differential in speed lest one tire scrub from being dragged.
The earliest of these “differential axles” was engineered by Renault from an idea conceived by the American auto maker, C.E. Duryea.
Thus began a layout that became a standard for decades to come – front engine with transmission in line, sending power back to a rear axle that split the force between the rear wheels by way of a differential. While relatively simple in design, that form factor had its downsides.
One of those was that when one of the rear wheels lost traction it would prevent the other from spinning due to the action of the differential. That led to the development of the Limited Slip Differential, typically known in automotive circles as an LSD or by any one of its manufacturer brand names like “Positraction,” “Sure Grip,” or “Twin Traction.”
The LSD works to ensure that a tire that has traction isn’t stymied by an opposite partner that has found itself lacking grip. This allows for faster launches, better application of power through corners and the ability to actually move away from a stop when one wheel is in the muck. It works by way of either mechanical effort – either torque-sensing or speed-sensing – or electronic control on some of the more complex modern cars.
Today a limited slip rear end is almost a requirement of any serious performance car, but it wasn’t always something that was offered, or promoted.  The company that first saw the value in touting an LSD as a performance add-on is one that’s no longer with us, even if its efforts as promoting the device still are.
From MotorEra:

Although differential locks were first used on a steam lorry in 1903 to provide wheel traction on slippery roads, it was not until 1956 that the first production limited-slip differential for a popular car was produced by Studebaker.

Studebaker used a Dana 44 limited slip rear axle, which they marketed as the “Twin Traction.” It first appeared on the Hawk, and found its way to the Lark, and the weird Packard Hawk, which was the rebranded Studebaker sold as that famous brand’s swan song model.
Studebaker may not have lasted, but its Twin Traction rear axle outlived the company, being made available on the Avanti II which was offered by South Bend Indiana Studebaker dealer Nate Altman when he bought the rights and tooling for the car in 1965.
Image: Wikipedia

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    1. smalleyxb122 Avatar

      Best scene in that movie. Best moment of Marissa Tomei’s career. That’s not to disparage the rest of the movie, or the rest of her career; That scene is just that great.

  1. dukeisduke Avatar

    Like I said in the new Ranchero thread, I like the Detroit True-Trac, as it’s a helical gear setup with no friction plates or cones to make noise, or wear out, and you don’t have to add friction modifier. I had one in my ’95 F-150 (the original pinion bearings wore out at 92k, from too much factory preload, so it was an excuse to add an LSD), and I loved it.
    Everyone had a trademark name for their LSD, and Pontiac’s was Saf-T-Track.

  2. I_Borgward Avatar

    Studebaker! I might have known. My guess was Jaguar.
    One of my Volvo 240s came with an optional factory LSD, a waste if you ask me considering the low output of the motor.
    When I got the car home and started to sort it out, I noted that the rear tires were different sizes, one taller than the other. I swapped them out for a matched set.
    A few months later on a long road trip, the rear of the car started to hop and thump like a giant rabbit every time I’d corner. Uh oh. That’s when I discovered the car had the LSD. Good thing interstates are mostly in a straight line.
    Who knows how long the previous owner drove with the mismatched height tires, but my theory is that’s what trashed the LSD and caused its clutches to grab and release on turns. I ended up swapping in the entire rear axle assembly from a junker to cure the problem.

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