THE CHEVROLET
TURBOGLIDE TRANSMISSION

1957 Chevy
 

The Turboglide transmission had the following design features:

1. The transmission has a torque converter with an impeller, three turbines, and a stator
2. This is combined with two planetary gearsets, four fluid controlled clutches, and three one-way sprag clutches.
3. Each of two of the turbines drives one of the planetary gearsets. The third drives the drive shaft directly
4. It does not shift gears as most transmissions shift gears. It phases between gears.
5. There is no active logic for gear selection in the valve body.
6. The pull on the drive wheels and the sprag clutches select the gear ratio.

    Sprag clutches are one-way clutches. They couple the shafts in one direction, and freewheel in the other direction.

7. The only time the valve body changes the clutches is when the gearshift is moved.
8. It behaves very similarly to the new Continuously Variable Transmission (CVT), but it works in a totally different way.
9. It's a shiftless transmission.
10. GM essentially had a CVT in the 1950s.

Turboglide angle section
 

Gearshift quadrant
 

I spent 21 years knowing the Turboglide.

• When I was 5 years old, my father bought a new 1957 Chevrolet with a Turboglide transmission. It was the first car with an automatic transmission my father ever had.
• My father was an engineer and deliberately chose this design over the others available.
• Four months later the transmission quit working. But GM had a recall on it, because the 2nd Turbines were breaking the spokes that centered them. The fix was to replace a 3-spoke design with a stronger 5-spoke design. This fixed the trouble.
• When I was 12 years old, I studied automatic transmissions. I knew how the Turboglide worked before I could drive it.
• When I was 17 years old, this 1957 Chevy was one of three cars I learned to drive in.
• This car was one of my all-time favorites.
• For most of the 21 years we had the car, the transmission gave us no trouble.
• In 1978, my brother was supposed to be on TV and there were no parking spaces left in the studio lot. So the director told him to park in his own space and if he got a ticket, he would pay the fine.
• Instead of issuing a ticket, the security guard had the car towed. The towing company didn't know there was a 25 mph limit for towing a Turboglide with the back wheels down. The transmission quit the next day because it was overheated by the tow.
• The insurance company totaled the car, but required that the car be forfeited to get the payment.

Characteristics I observed in the Turboglide.

• Unless the car is actually accelerating or otherwise loaded, the transmission operates in direct drive.
• The Turboglide responds instantly to throttle variations and road load. There is no waiting for condition detection or transmission control logic to act.
• When you needed the power, it was immediately there.
• The Turboglide is the smoothest transmission I ever drove.
• Unlike other transmissions, I almost never found the Turboglide doing something I didn't want it to do.
• Even in winter driving conditions, it did not often spin the wheels when the throttle was used lightly.

   This is because it stays in direct drive until torque is demanded.

• If using Turboglide in D caused wheel spin on snow or ice, GR worked with very low throttle to get the car past icy obstacles at low speed.
• I have driven two CVT cars, and neither was as smooth as the Turboglide. I had to wait on the transmission control logic and servos.

If given an otherwise equal choice, I would buy a car with the equivalent of a Turboglide over a CVT or any other car.

Turboglide ad
 

Real Turboglide
 

I have seen two ads intended to sell the concept of the Turboglide.
  They were animated cartoons with drawings of three turbines (right).

Both cartoons showed each of the three turbines active at powering the car while the other two turbines were stopped.

That is NOT how Turboglide works.

My edited image at the bottom is a better rendition.
 - In the first part, the 1st Turbine spins faster than the others.
 - In the second part, the 1st and 2nd Turbine spin faster than the other one.
 - In the third part, all three turbines spin at the same speed.

As the car accelerates, Turboglide's turbines work as follows:

• When the car is stopped (in drive), all three turbines are stopped because all three are trying to turn the car wheels.
• As the car takes off, all three turbines start turning, with their rotation rates corresponding to the gear ratios of their gears.
• When the car is taking off from a stop, the 1st Turbine is turning fastest.
• The rotation rate of the 1st Turbine increases until it is turning the same speed the impeller is turning.

    Then it cannot turn any faster.

• When the car accelerates beyond the 1st Turbine maximum rate, the 1st Turbine sprag clutch disengages.

   The 1st Turbine continues to turn at the speed of the impeller while the 2nd Turbine takes over moving the car.

• The rotation rate of the 2nd Turbine increases until it is turning the same speed the impeller is turning.

    Then it cannot turn any faster.

• When the car accelerates beyond the 2nd Turbine maximum rate, the 2nd Turbine sprag clutch disengages.

   The 2nd Turbine continues to turn at the speed of the impeller while the 3rd Turbine takes over moving the car.

• The rotation rate of the 3rd Turbine increases until it is turning the same speed the impeller is turning.

    Then it cannot turn any faster.

• Now all three turbines are turning the same speed, but the 3rd Turbine is moving the car.

   This happens no matter what speed the driver is driving.

This table shows the relative speeds of the turbines for the various phases of operation.

Philco M22
Manual 7, 10, & 12-inch
Turn shelf to select size
≈ Manual transmission
 

Garrard AT-6
Automatic 7, 10, & 12-inch
Dropped record moves sensor
≈ 3 speed Turbo Hydramatic
 

Collaro Conquest
Any size 12-inch to 6-inch
Arm measures exact size
≈ Turboglide
 

The page author noticed the similarities in design philosophies between transmissions and other technologies. Here are some of those similarities:

• Record Changers

  Various designs of record changers seem to have analogs to automotive transmissions:

  1. Manual transmissions are like changers with manual size selection.
  2. Automatic transmissions are like changers with automatic size sensing.
  3. Turboglide is like a changer that senses the exact size of the record.
• Traffic signals

  Various designs of traffic signals seem to have analogs to automotive transmissions:

  1. Manual transmissions are like pretimed signals that always do the same thing.
  2. Automatic transmissions are like signals with small sensors and extension timers.
  3. Turboglide is like a signal with large-area sensors for rapid response.