Turboglide
Encyclopedia
The Turboglide is a Chevrolet
constant torque automatic transmission
that made its debut as an optional transmission on Chevrolet V8
passenger cars for 1957. It consisted of a concurrently geared (as opposed to sequentially geared) planetary gearbox with a 'switch pitch' dual pitch torque converter stator. Turboglide utilized a die-cast aluminum transmission case, following Packard
's Ultramatic
of 1956. It was designed to help showcase the engineering features of the '57 Chevy
, and was often ordered with the Rochester RamJet
Fuel Injection
system on the 283 V8
. Turboglide cost about $50 more than Powerglide
, and was available in all 1957-1961 V8 engine models except the Corvette
.
Turboglide was modeled along the lines of the Buick Flight Pitch Dynaflow
transmission, and operated very similarly to the Buick
transmission. Using a five element torque converter
, (pump, individual turbines for low, intermediate and direct ranges, and a switch pitch stator
) the Turboglide offered the smoothest operation of any automatic in the industry, as no 'shift' occurred between ranges and hence there was no potential to create a disruption in the perfectly smooth flow of power. For extra 'getaway' power at any road speed, the converter stator vanes could be directed to a steeper angle which raised the stall speed of the torque converter and increased torque multiplication, as well as directing the oil flow at the turbine for the next lowest range. Turboglide's selector quadrant was Park, Reverse, Neutral, Drive, Hill Retarder(1957 only) P R N D Hr or Grade Retarder.(1958-1961) P R N D Gr.
. Most automatic transmissions have a three element torque converter, consisting of an impeller, which is an engine driven pump turbine that rotates with the flywheel
, a transmission drive turbine that receives the energy of the oil propelled by the impeller, and a stator that redirects the recirculating oil so that it strikes the back side of impeller blades to assist engine rotation and recapture energy from the fast moving oil. The stator is what gives the torque converter its torque multiplication ability — in effect allowing it to reduce ratio to increase torque when the turbine is rotating slower than the pump.
In most automatic transmissions, the drive turbine only functions as an input to the transmission where the power is redirected to gears in its automatic gearbox. Turboglide differs by using three individual drive turbines, each connected to a different ratio inside the gearbox. Oil leaving the pump first strikes the turbine connected to the Low (first gear) ratio. The design of the turbine permits oil to pass through its blades and strike the next turbine in line, the one connected to the Intermediate ratio, which receives some of the energy remaining in the oil flow. After leaving the intermediate turbine, the oil is passed to the direct turbine which is direct drive at driveshaft
speed. As the car starts from rest, the low turbine, which has the greatest gear reduction ratio is relatively easy to bring up to match pump (engine) speed and the car starts from rest easily and accelerates quickly. While this occurs, the intermediate turbine receives an ever increasing share of the energy from the pump, as the Low turbine moves faster and oil passes more freely through it. Eventually, the low turbine matches pump speed, and the low turbine freewheels on a one way 'sprag-clutch
' much like on a bicycle. At this point, the intermediate turbine is carrying the majority of the drive force, and some energy is being sent to the direct turbine from the oil passing through the intermediate turbine as it also begins to match pump speed. Eventually, the intermediate turbine also matches pump speed, and the oil passes freely through low and intermediate turbines to drive the direct turbine alone, in direct drive (1:1 ratio). Because of the overlapping power input in different ratios, there is no 'shift' or sequential gearing, rather there is a concurrent geared drive, in effect the car starts out in 1-2-3, eventually drops 1 to be in 2-3 and eventually drops 2 to be in 3 alone.
The stator element of the torque converter has two blade positions, controlled by the driver via the accelerator pedal to offer a 'passing gear' and extra response at any speed from heavy throttle application. In normal driving the stator blades are arranged at 'cruise' angle which offers improved efficiency and response at light throttle. Flooring the accelerator pedal changes the angle of the stator vanes hydraulically to 'performance angle' which permits the converter to achieve stall about 1000 rpm higher than in 'cruise' as well as redirecting oil to strike the next-lowest drive turbine which effectively lowers the drive ratio of the transmission and allows engine speed to flare to a speed where output is greatest.
Because of its unique operating characteristics, Turboglide did not require large changes in engine RPM even with very large differences in car speed or desired engine output. In fact, accelerating from rest, the engine speed would remain nearly constant(with no movement of the accelerator), even as the vehicle accelerated. The actual RPM would be a function of the pressure applied to the accelerator. One interesting effect during acceleration was the "audio" transition from the first gear turbine (occurring about 2 seconds after takeoff with moderate throttle), then progressing through the remaining 2 turbines which were not so audible. (A similar audio effect occurs with a stepped 3-speed automatic...first gear having a characteristic whine).
At full throttle, Turboglide will maintain the engine RPM within a narrow (~400 rpm) span of speed around 3500-4000 rpm where best engine output is maintained, and the car will slingshot to catch up as the ratios drop imperceptibly as the car road speed increases. The effect is very similar to a jet aircraft upon takeoff- the engine maintains a strong high speed, and the car accelerates smoothly and strongly from rest to maximum. In normal light traffic driving, Turboglide automatically selects the highest (lowest numerically) ratio practical and engine speeds run in the 1000-2500 rpm range, saving fuel and improving the throttle response of the car to small pedal motions. Turboglide also offered a 'Grade Retarder' range for engine braking which could absorb close to 200 hp of energy above what was available via engine compression, by counter-rotating the turbines in the converter and soaking up vehicle energy by agitating the oil inside the converter housing. No low range was provided with Turboglide, as in Drive range the ratio was always automatically matched perfectly to the requirements of the operator (all ranges being always engaged, low and intermediate would freewheel on the 'sprag-clutch
es' as needed), and Grade Retarder made a very efficient engine brake.
Continuously Variable Transmission
s (CVT), which are available in some smaller cars, offer a similar, albeit completely mechanical, feel.
and Robert P Benzinger at Chevrolet engineering. Although Turboglide offered remarkable performance and smoothness, the execution of the first 1957 units led to substantial customer complaints and the unit was continuously upgraded to improve its durability until it was discontinued in 1961. The 1959 Turboglide incorporated very significant changes intended to improve its durability, some of which were possible to retrofit to earlier versions.
Chevrolet
Chevrolet , also known as Chevy , is a brand of vehicle produced by General Motors Company . Founded by Louis Chevrolet and ousted GM founder William C. Durant on November 3, 1911, General Motors acquired Chevrolet in 1918...
constant torque automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...
that made its debut as an optional transmission on Chevrolet V8
Chevrolet Small-Block engine
The Chevrolet small-block engine is a series of automobile V8 engines built by the Chevrolet Division of General Motors using the same basic small engine block...
passenger cars for 1957. It consisted of a concurrently geared (as opposed to sequentially geared) planetary gearbox with a 'switch pitch' dual pitch torque converter stator. Turboglide utilized a die-cast aluminum transmission case, following Packard
Packard
Packard was an American luxury-type automobile marque built by the Packard Motor Car Company of Detroit, Michigan, and later by the Studebaker-Packard Corporation of South Bend, Indiana...
's Ultramatic
Ultramatic
For the Voigtländer SLR camera, see Voigtländer Ultramatic CSUltramatic was the trademarked name of the Packard Motor Car Company's automatic transmission introduced in 1949 and produced until 1956 at Packard's Detroit, Michigan factory....
of 1956. It was designed to help showcase the engineering features of the '57 Chevy
57 Chevy
The 1957 Chevrolet is an automobile which was introduced by the Chevrolet division of General Motors in September, 1956. It was available in three series models: the upscale Bel Air, the mid-range "two-ten", and the "one-fifty". A two-door station wagon, the Nomad was produced as a Bel Air model....
, and was often ordered with the Rochester RamJet
Ramjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
Fuel Injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....
system on the 283 V8
Chevrolet Small-Block engine
The Chevrolet small-block engine is a series of automobile V8 engines built by the Chevrolet Division of General Motors using the same basic small engine block...
. Turboglide cost about $50 more than Powerglide
Powerglide
The Powerglide is a two-speed automatic transmission designed by General Motors. It was available primarily on Chevrolet from January, 1950 through 1973, although some Pontiac models also used this automatic transmission, extensively on models produced for the Canadian market with Chevrolet...
, and was available in all 1957-1961 V8 engine models except the Corvette
Chevrolet Corvette
The Chevrolet Corvette is a sports car by the Chevrolet division of General Motors that has been produced in six generations. The first model, a convertible, was designed by Harley Earl and introduced at the GM Motorama in 1953 as a concept show car. Myron Scott is credited for naming the car after...
.
Concept
ChevroletChevrolet
Chevrolet , also known as Chevy , is a brand of vehicle produced by General Motors Company . Founded by Louis Chevrolet and ousted GM founder William C. Durant on November 3, 1911, General Motors acquired Chevrolet in 1918...
Turboglide was modeled along the lines of the Buick Flight Pitch Dynaflow
Dynaflow
Dynaflow was the trademark name for a type of automatic transmission developed and built by General Motors' Buick Motor Division from the late 1940s to the mid 1963...
transmission, and operated very similarly to the Buick
Buick
Buick is a premium brand of General Motors . Buick models are sold in the United States, Canada, Mexico, China, Taiwan, and Israel, with China being its largest market. Buick holds the distinction as the oldest active American make...
transmission. Using a five element torque converter
Torque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...
, (pump, individual turbines for low, intermediate and direct ranges, and a switch pitch stator
Stator
The stator is the stationary part of a rotor system, found in an electric generator, electric motor and biological rotors.Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the...
) the Turboglide offered the smoothest operation of any automatic in the industry, as no 'shift' occurred between ranges and hence there was no potential to create a disruption in the perfectly smooth flow of power. For extra 'getaway' power at any road speed, the converter stator vanes could be directed to a steeper angle which raised the stall speed of the torque converter and increased torque multiplication, as well as directing the oil flow at the turbine for the next lowest range. Turboglide's selector quadrant was Park, Reverse, Neutral, Drive, Hill Retarder(1957 only) P R N D Hr or Grade Retarder.(1958-1961) P R N D Gr.
Operation
The basis of Turboglide's unique abilities was its five-element torque converterTorque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...
. Most automatic transmissions have a three element torque converter, consisting of an impeller, which is an engine driven pump turbine that rotates with the flywheel
Flywheel
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia, and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed...
, a transmission drive turbine that receives the energy of the oil propelled by the impeller, and a stator that redirects the recirculating oil so that it strikes the back side of impeller blades to assist engine rotation and recapture energy from the fast moving oil. The stator is what gives the torque converter its torque multiplication ability — in effect allowing it to reduce ratio to increase torque when the turbine is rotating slower than the pump.
In most automatic transmissions, the drive turbine only functions as an input to the transmission where the power is redirected to gears in its automatic gearbox. Turboglide differs by using three individual drive turbines, each connected to a different ratio inside the gearbox. Oil leaving the pump first strikes the turbine connected to the Low (first gear) ratio. The design of the turbine permits oil to pass through its blades and strike the next turbine in line, the one connected to the Intermediate ratio, which receives some of the energy remaining in the oil flow. After leaving the intermediate turbine, the oil is passed to the direct turbine which is direct drive at driveshaft
Driveshaft
A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
speed. As the car starts from rest, the low turbine, which has the greatest gear reduction ratio is relatively easy to bring up to match pump (engine) speed and the car starts from rest easily and accelerates quickly. While this occurs, the intermediate turbine receives an ever increasing share of the energy from the pump, as the Low turbine moves faster and oil passes more freely through it. Eventually, the low turbine matches pump speed, and the low turbine freewheels on a one way 'sprag-clutch
Sprag
A sprag clutch is a one-way freewheel clutch. It resembles a roller bearing, but instead of cylindrical rollers, non-revolving asymmetric figure-of-eight shaped sprags are used...
' much like on a bicycle. At this point, the intermediate turbine is carrying the majority of the drive force, and some energy is being sent to the direct turbine from the oil passing through the intermediate turbine as it also begins to match pump speed. Eventually, the intermediate turbine also matches pump speed, and the oil passes freely through low and intermediate turbines to drive the direct turbine alone, in direct drive (1:1 ratio). Because of the overlapping power input in different ratios, there is no 'shift' or sequential gearing, rather there is a concurrent geared drive, in effect the car starts out in 1-2-3, eventually drops 1 to be in 2-3 and eventually drops 2 to be in 3 alone.
The stator element of the torque converter has two blade positions, controlled by the driver via the accelerator pedal to offer a 'passing gear' and extra response at any speed from heavy throttle application. In normal driving the stator blades are arranged at 'cruise' angle which offers improved efficiency and response at light throttle. Flooring the accelerator pedal changes the angle of the stator vanes hydraulically to 'performance angle' which permits the converter to achieve stall about 1000 rpm higher than in 'cruise' as well as redirecting oil to strike the next-lowest drive turbine which effectively lowers the drive ratio of the transmission and allows engine speed to flare to a speed where output is greatest.
Because of its unique operating characteristics, Turboglide did not require large changes in engine RPM even with very large differences in car speed or desired engine output. In fact, accelerating from rest, the engine speed would remain nearly constant(with no movement of the accelerator), even as the vehicle accelerated. The actual RPM would be a function of the pressure applied to the accelerator. One interesting effect during acceleration was the "audio" transition from the first gear turbine (occurring about 2 seconds after takeoff with moderate throttle), then progressing through the remaining 2 turbines which were not so audible. (A similar audio effect occurs with a stepped 3-speed automatic...first gear having a characteristic whine).
At full throttle, Turboglide will maintain the engine RPM within a narrow (~400 rpm) span of speed around 3500-4000 rpm where best engine output is maintained, and the car will slingshot to catch up as the ratios drop imperceptibly as the car road speed increases. The effect is very similar to a jet aircraft upon takeoff- the engine maintains a strong high speed, and the car accelerates smoothly and strongly from rest to maximum. In normal light traffic driving, Turboglide automatically selects the highest (lowest numerically) ratio practical and engine speeds run in the 1000-2500 rpm range, saving fuel and improving the throttle response of the car to small pedal motions. Turboglide also offered a 'Grade Retarder' range for engine braking which could absorb close to 200 hp of energy above what was available via engine compression, by counter-rotating the turbines in the converter and soaking up vehicle energy by agitating the oil inside the converter housing. No low range was provided with Turboglide, as in Drive range the ratio was always automatically matched perfectly to the requirements of the operator (all ranges being always engaged, low and intermediate would freewheel on the 'sprag-clutch
Sprag
A sprag clutch is a one-way freewheel clutch. It resembles a roller bearing, but instead of cylindrical rollers, non-revolving asymmetric figure-of-eight shaped sprags are used...
es' as needed), and Grade Retarder made a very efficient engine brake.
Continuously Variable Transmission
Continuously variable transmission
A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios...
s (CVT), which are available in some smaller cars, offer a similar, albeit completely mechanical, feel.
History
Turboglide was designed under the supervision of Frank Winchell, Ed ColeEd Cole
Edward Nicholas Cole was an American automotive executive for General Motors.- Career :Cole was the son of a dairy farmer. In his youth, he designed, built, and sold homemade radio sets, and as a teenager became a field representative for a tractor manufacturer...
and Robert P Benzinger at Chevrolet engineering. Although Turboglide offered remarkable performance and smoothness, the execution of the first 1957 units led to substantial customer complaints and the unit was continuously upgraded to improve its durability until it was discontinued in 1961. The 1959 Turboglide incorporated very significant changes intended to improve its durability, some of which were possible to retrofit to earlier versions.