1961 Buick Electra 225 / RM Sotheby’s
The auction listing for this attractive Tampico Red 1961 Buick Electra 225 convertible claims that it has a “column-shifted two-speed automatic transmission.” As you may already know if you’re a Buick fan, this isn’t correct, and it’s a common misconception about the Turbine Drive transmission — last iteration of Buick’s long-serving Dynaflow line. Let’s take a closer look at Turbine Drive, which was not a two-speed automatic, but rather a continuously variable transmission.
From 1948 through 1963, Buick designed and built its own automatic transmissions. I’ve previously written about the unusual two-speed Dual-Path Turbine Drive used in the 1961–1963 Buick Special and Skylark, but I wanted to talk more about the transmissions used in the full-size Buicks CC readers are more likely to be familiar with, including the 1963 Buick Riviera.
The listing for this handsome blue 1963 Riviera claims it has a three-speed automatic, which is wrong unless someone has retrofitted a later Turbo Hydra-Matic / Gooding & Company
Buick’s very complex three-turbine automatic, known as Flight Pitch Dynaflow or Triple Turbine, is a subject for another post: What we’re concerned with here is the 1956 through 1963 twin-turbine transmission, which Buick called Variable Pitch Dynaflow, then Twin Turbine, and finally Turbine Drive. (There are some minor differences between the transmissions of different model years, but the operating principles and major components of the 1956 and later twin-turbine transmissions are substantially the same.)
1961 Buick brochure / Old Car Manual Project Brochure Collection)
Very nearly all full-size Buicks of this era used the twin-turbine automatic. In some years, you could still theoretically order a three-speed manual transmission on the cheaper models, but it was very, very rare, and buyers in 1958 and 1959 were rightfully wary of the buggy, expensive three-turbine transmission. So, if you see a big Buick of this era that still retains its original powertrain, it almost certainly has Variable Pitch Dynaflow/Twin Turbine/Turbine Drive. (For simplicity, I’m just going to call it “Turbine Drive” from here on.)
Turbine Drive was standard even on the low-line Buick LeSabre for 1961 / Mecum Auctions
If you look at the Turbine Drive transmission in cross-section, you’ll see that it has a Ravigneaux epicyclic gearset, similar to the one found in an iron-case Chevrolet Powerglide. However, it includes NO provision for automatic gear changes: It’s a planetary-geared manual transmission providing low, direct drive, reverse, and neutral. In Drive, the direct clutch engages and stays engaged, at all speeds and throttle positions.
1962 Buick Turbine Drive (Twin Turbine), from the 1962 service manual
Like most automatic transmissions with torque converters, Turbine Drive has an engine-driven centrifugal converter pump, which is bolted to the engine flywheel and always turns at engine speed. With the engine running, the rotation of the pump forces some of the oil in the converter housing through its vanes, from the center outward. Since the inner surface of the pump is curved, this impels the oil outward as a kind of rotating hollow cylinder.
Opposite the pump, facing towards the back of the car, is a squat metal cylinder that loosely resembles a small alloy wheel. This is the turbine support assembly, which contains the torque converter’s two turbines and one of its two stators. Between the turbine housing and the converter pump sits a smaller vaned wheel — the other of the two stators. Here’s a photo of the actual components:
Pieces of a 1957 to 1960 Twin Turbine/Turbine Drive torque converter — clockwise from top right: converter pump, front stator, converter cover, turbine support assembly / d2_willys — AACA Forums
Here’s an exploded view of the torque converter components:
From the service manual for the 1958 Buick Variable Pitch Dynaflow
The top of the turbine housing assembly is the first turbine, which has a narrow row of inlet vanes that sit directly opposite the outlet vanes of the converter pump. Here’s what the first turbine looks like when removed from the assembly:
First turbine of a 1956 Variable Pitch Dynaflow, from a Buick technical paper
Behind the first turbine sits the first stator, which has a similar row of inlet vanes around the rim. Although it’s not easy to see in these pictures, the vanes are angled in the opposite direction of the first turbine’s vanes.
From the 1962 service manual
Behind the first stator is the second turbine, which has its inlet vanes around its outer edge and its outlet vanes around the central hub. (The second stator sits in the space between those second turbine outlet vanes and the hub of the converter pump.)
Second turbine of a 1956 Variable Pitch Dynaflow, from a Buick technical paper
An important detail that’s not very easy to see in these blotchy scans is that the cylindrical turbine support housing and the second turbine are geared together, with their own set of planetary gears. The light-colored disc on the bottom of the second turbine in the photo below is the planet carrier, which contains four planet pinions. These mesh with the ring gear in the bottom of the turbine support housing; if you squint, you can just make out the gear teeth. The reaction sun gear is on the other side of the second turbine, mounted on an overrunning clutch in the hub of the turbine assembly. The planet carrier is bolted to the underside of the second turbine, and is also splined to the output shaft. The ratio of this gearset is 1.6 to 1.
From the 1962 service manual
Here’s a labeled diagram, which I fear will not help very much than the grainy shop manual photo above. (In an ideal world, I would show you color photos of the actual components, but since I don’t have a Turbine Drive transmission I can take apart for that purpose, this will have to suffice.)
Cutaway of the 1956 Variable Pitch Dynaflow, from a Buick technical paper (note that the first stator is called the “outer stator”)
So, now that you have an approximate sense of the components, what actually happens when you sit down in your 1961 Electra 225 or 1963 Riviera, move the gear selector to “D,” and press the accelerator?
Turbine Drive shift quadrant in a 1961 Buick Electra 225 / RM Sotheby’s
As engine speed increases, the converter pump creates a rotating column of moving oil. This leaves the pump rim and enters the first turbine. The oil passes through the first turbine’s vanes into the first stator, and then into the second turbine. Oil then leaves the second turbine and passes through the front stator before returning to the pump to start the cycle again. In the process, it transmits and — sometimes — multiplies the engine’s torque.
We tend to think of a torque converter as a clutch rather than a transmission in its own right, but it’s really a type of CVT, capable of multiplying input torque much like mechanical reduction gears. All it needs is a reaction member that can redirect the oil flow, providing some additional mechanical leverage during acceleration, and then get out of the way when it’s not needed. Below is a typical automotive converter, with a stator mounted on an overrunning clutch that lets it spin freely in the direction of engine rotation, but locks the stator to the transmission case if it moves in the opposite direction:
Diagram from a Buick technical paper
However, as I just explained, the Turbine Drive converter is much more complicated than the more basic three-element unit shown above. On the Buick transmission:
- There are two turbines, not one.
- The second turbine is splined to the output shaft.
- The first turbine is geared to the second (and the output shaft) by planetary gears.
- The reaction member of that planetary gearset (the sun gear) is on an overrunning clutch.
- There’s a stator between the two turbines, also mounted on an overrunning clutch.
- There’s another stator between the second turbine and the converter pump. This has variable-pitch blades, which we’ll get to a little later.
Let’s consider what happens when starting from rest. The converter pump is bolted to the engine flywheel, so it turns at engine speed and (on a Buick “Nailhead” V-8 engine) in a clockwise direction. With the car stationary, the output shaft isn’t moving, so both turbines are also stationary (stalled).
The rotating column of oil from the converter pump enters the first turbine and applies torque to it. That torque is multiplied by the planetary gears and applied to the second turbine and the output shaft. As the moving oil applies torque to the first turbine, the reaction force changes the direction of the oil’s rotation, so its rotary flow is now in the “wrong” direction: counterclockwise. This oil next enters the first stator, whose overrunning clutch only allows it to turn clockwise. The force of the oil spinning in the other direction locks the stator in place, redirecting the oil back in the “correct” clockwise direction before it enters the second turbine.
Diagram from a Buick technical paper showing the reversals of the moving oil’s direction of rotation
The second turbine is also stationary, so as the moving oil strikes its blades, the reaction once again reverses the direction of the oil’s rotary flow. This means the oil is again rotating in a counterclockwise direction when it leaves the second turbine and hits the second (variable-pitch) stator, locking that stator against its clutch and redirecting the oil in a clockwise direction so that it won’t try to brake the engine’s rotation when it reenters the pump. This series of redirections causes the oil to reenter the converter pump with more force than the engine generates, multiplying engine torque. With this layout, the converter’s “torque ratio” is a little over 3 to 1 when starting from rest, equivalent to a low gear of 3.10:1 when starting at part-throttle.
Service manual diagram illustrating the converter’s action during initial acceleration, from the 1962 service manual
In any torque converter, the amount of torque the converter pump can apply to a turbine depends on their relative speeds, and is greatest when the pump is moving and the turbine is stationary. As the first turbine speeds up and the torque on it diminishes, the reaction force also diminishes, until eventually oil just passes through the first turbine vanes without changing directions, which causes the first stator to freewheel. After a while, the oil is applying more torque to the second turbine than the first, which causes the reaction sun gear of the planetary gears connecting the turbines to freewheel. Once that happens, the first turbine can no longer transmit any torque, so it also freewheels, while the second turbine speeds up until it’s turning at almost but not quite engine speed. From there, the converter is simply acting as a fluid clutch, not multiplying any torque, equivalent to a gear ratio of about 1:1.
Service manual diagram showing converter action at cruising speed, from the 1962 service manual
Unlike mechanical gears, where the gearing creates a fixed relationship between engine speed and road speed in each gear, the Turbine Drive converter (or really any torque converter) will always “seek” that 1:1 stage, whether cruising at 70 mph on the interstate or toddling along in a parking lot at a walking pace. Once the converter gets to that stage (which engineers call the coupling stage), it will only start multiplying torque again if there’s a significant difference in the speeds of the engine and the output shaft. For example, if you step on the gas to accelerate, or if the car slows due to climbing a steep hill, engine speed will increase relative to output shaft speed, which may be enough to get the converter back into its torque multiplication range. (Note that these Buick transmissions do not have any torque converter lockup clutch.)
In these transmissions, there’s a second stator that sits roughly in the center of the converter assembly, between the second turbine outlets and the converter pump inlets. When the converter is running close to its 1:1 coupling stage, this stator freewheels. If there’s a big enough speed difference between the pump and second turbine, due to acceleration or increased load, oil leaving second turbine will have a counter-clockwise rotation, which will lock the stator and provide additional torque multiplication. With the car in motion, this multiplication will never be as great as when starting from rest, but it provides a little extra leverage, akin to downshifting to a lower gear.
The 1956 variable-pitch stator as pictured in a Buick technical paper; the left photo shows the blades at high angle, the right photo at low angle
This is where the stator’s variable-pitch function comes into play. In most normal driving, the blades stay at their low angle (pictured above right), which is more efficient for cruising. However, if you press the accelerator pedal all the way to the floor, a mechanical linkage closes a hydraulic control valve and causes the variable-pitch stator blades to crank open, much like a set of Venetian blinds. Moving the blades to a higher angle increases their ability to redirect oil flow and multiply torque, giving extra kick for passing acceleration. Once the second turbine speed has almost caught up with the pump, the stator will still freewheel as normal, and releasing the accelerator will cause the blades to return automatically to their low angle.
This stator “kickdown” is important because it’s the only provision Turbine Drive makes for passing at highway speeds. It also provides better acceleration on a full-throttle start: If you floor the accelerator, the stator blades will start at their high angle, giving a starting torque ratio of 3.4, equivalent to a low gear of 3.40:1. (This also raises the stall speed by around 200 rpm, letting the engine rev up a bit more before the car takes off.)
From the 1962 service manual
With the selector in D, that is basically it: The planetary transmission behind the converter stays locked in direct drive (1.00:1), while the converter provides a variable ratio ranging from 3.40 to 1.00 to one. That’s adequate for most normal driving, but you can get better acceleration if you manually select L range, which adds the planetary transmission’s 1.82:1 mechanical reduction gear to the multiplication provided by the converter. However, you have to move the selector back to D to return to direct drive. Depending on the axle ratio, you can stay in L up to 55 to 65 mph, but the manuals warn very sternly that you should not shift from D to L over 40 mph, lest you damage the transmission.
Turbine Drive console shifter in a 1963 Buick Riviera / Mecum Auctions
Unlike the earliest (1948–1952) Dynaflow transmissions, Turbine Drive is really not particularly slushy. That was the whole point of the multiple stages and planetary gears, which increase the converter’s efficiency while also allowing more torque multiplication than even a very “loose” high-stall three-element converter. You do sacrifice some off-the-line acceleration when starting in D, but performance is still adequate for most situations, and you’re less likely to spin the drive wheels on launch. The payoff is that operation in D is completely seamless: Most of the transitions between the converter’s various stages aren’t normally perceptible at all. The only “shift” you’re likely to notice in D is the variable-pitch stator “kickdown,” and that’s as much due to the mechanical action of the detent (which you can feel as added resistance towards the bottom of the accelerator pedal travel) as the change in converter action.
1961 Buick Electra 225 / RM Sotheby’s
Turbine Drive is big and fairly heavy, and Buick admitted that its additional stages do penalize cruising efficiency a little (even freewheeling, the additional turbine and stator cause a bit of extra fluid drag). However, while the later Turbo Hydra-Matic (Super Turbine 400, as Buick called it) is more flexible and a little more efficient, it can’t match the old Turbine Drive for smoothness or distinctive Buick character.
Related Reading
CC Tech: More on the Buick Dual-Path Turbine Drive Transmission – Asking “Why” As Well As “How” (by me)
CC Tech: 1961–1963 Buick Dual-Path Turbine Drive Transmission – Forward Thinking About Going Backwards (by me)
Dynaflow, Turboglide, Roto Hydra-Matic, and Other Early GM Automatics (at Ate Up With Motor)
Curbside Capsule: 1960 Buick Invicta Convertible – I Feel Just Fine, Thank You (by Joseph Dennis)
Car Show Classics: 1960 Buicks – If This Is A Slump, What Is A Streak? (by Aaron65)
Car Show Classic: 1960 Buick LeSabre Convertible – I’d Really Rather Have This (by Laurence Jones)
Curbside Classic: 1961 Buick LeSabre Sedan – Aqua Time Machine (by Tom Klockau)
Vintage Car Life Road Test: 1962 Buick Wildcat Sport Coupe – A B-Body Buick Joins The Bucket Brigade (by me)
Vintage Motor Trend Road Test: 1963 Buick Riviera – Hot Rod Nailhead Buick (by Paul N)
Auction Classic: 1964 Buick Wildcat – A Dual-Quad 425 “Nailhead” V8 and Four-Speed Stick Make This Cat A Sleeper (by Paul N)
I don’t know if this was a factor in its demise, as the “unconventional” shift pattern (by modern standards), that placed Reverse below First Gear in the shift quadrant was outlawed by NHTSA in 1966, forcing the more conventional PRNDL shift pattern that has become the standard for all automatic transmissions, no matter how many forward speeds are available. All I know is that all two-speed automatic transmissions have since been supplanted by three-speed units, and indeed, even three forward speeds have become obsolete, as some modern automatic transmissions now have up to nine (9) speeds!
Nah, the Turbine Drive was long gone by the time MVSS 102 was promulgated, and if that had been a concern, it would have been trivial to redesign the valve body to separate Low and Reverse. The reason they were frequently adjacent was so that you could “rock” the drive wheels free of mud or snow by moving rapidly back and forth from Low to Reverse. Nearly all of the early GM automatics did that; the main exceptions were the triple-turbine transmissions, which didn’t have a Low range. (Chevrolet switched Powerglide to PRNDL after Turboglide was introduced because they were worried that having two different shift patterns in Chevrolet cars would be confusing.)
Does anyone know how the first and second turbine are manufactured? Looking at them I would assume they are dip brazed but that is labor intensive. Maybe they are cast?
The first turbine was a semi-permanent mold aluminum casting (low-pressure die casting, using one-piece cores). The second turbine originally was also, but Buick found it was cheaper to use a sheet-metal assembly, and since the sections could be thinner than aluminum, it weighed the same.
This is the core used for casting the first turbine:
thank you
if the 2nd turbine was sheet metal then it would have been assembled using dip or oven brazing.
People will characterize the early 60’s Buick transmissions as a detriment to performance, again remembering the old Dynaflows of the early 50’s.But we should look close at Buick’s record in NHRA D/SA racing, Pops Kennedy was near unbeatable in 55,56,57 Centuries, and then again in a 59 and 61 Invicta’s. In fact he won the 62 Indy Nationals in the 61 Invicta. The Dyna Flow proved to be more than competative against the Slim Jim Pontiacs, Rotomatic Oldsmobiles, Hydramatic Cadillacs and Cruise-O-Matic Fords and Torque-Flite Chrysler products.
An interesting read with my morning coffee. Might need a second cup to digest it all though, quite a different transmission.
GM sure wasn’t afraid to try new things or let each division go off in a different direction at the time. I’ve often wondered if all these different automatic transmissions, none of which lasted long in production, hastened the scrappage of these cars. It must have been hard to find someone to fix these, or a Turboglide, or a Roto Hydramatic after a few years!
My father had a ’61 Invicta convertible (medium green, light green top & dark, medium & light green interior!). Took my driver license test in it and loved that car. Unfortunately he traded it in on a ’62 Electra 225 convertible the next year 🙁
I didn’t follow you all the way into the deep weeds in this article but that 1961 Buick Electra 225 convertible in Tampico Red sure is pretty.
My wife briefly owned a Jeep Patriot with a JATCO CVT. Driving it reminded me of older Buicks I had once owned.
I never thought of the Dynaflow (or whatever name Buick gave it in different years) as a CVT, but your comparison to a CVT makes a lot of sense.
Full throttle acceleration certainly imparted a similar sensation. Engine revs spun up quickly. Acceleration eventually followed.
Hard to compare memories fairly since my Buick ownership is so much further in the past than the Jeep Patriot.
I give the nod to the Buick based on subjective feel. Buicks felt smooth and powerful even if not particularly fast. The Patriot came across as agricultural in nature.
My father had a 1962 Le Sabre. I thought it also had the single speed dual path turbine drive transmission. But AI research tells me otherwise.
Just a 2 speed “powergilde”.
According to this brochure for 1962 full-sized Buicks, the LeSabre had Turbine Drive as standard equipment. True also for Canada. No sign of a Powerglide anywhere.
https://oldcarbrochures.com/static/NA/Buick/1962_Buick/1962%20Buick%20Full%20Size%20Brochure/index1.html
I would characterize the 50s and 60s as the experimental period of automatic transmission with trick torque converters, fluid couplings and interesting shift mechanisms before things settled down in the 70s. There were also multiple torque converter heavy duty automatics like the ones in “fishbowl” busses and Budd railcars. By the 70s everyone was using the same basic torque converter, planetary gear sets and valve body, although we have added more gears over time.
My father came of driving age during WWII. Living in NYC, his first few years were spent driving pre-war heaps purchased for $25-$50, complete with unsynchronized 3-speed manual transmissions. In NYC traffic.
People like him could not wait to relieve themselves of the chore of shifting a car. It was of no matter to them whether automatics had poorer performance, used more gas, or weren’t as durable, they just wanted not to shift a car.
The moment he could scrape enough money together to buy his first new car (car loans weren’t really a thing at that time) he marched into a Chevrolet dealer and picked out a 1952 Bel Air with power steering, power brakes and Powerglide.
I’m curious as to how much power it took to operate the transmission and how it compared to other automatic transmissions at the time.
Buicks’ DynaFlow of the 1940’s was a huge leap in convenience and smoothness. From what I’ve read, the name came into popular usage as a descriptive term. Like, that jazz riff was DynaFlow, man! Buick’s big thing was smoothness, with straight eights and their DynaFlow automatic transmission. The Cadillac Hydramatic was a better performer, but had harder shifts. Trying to find a shop that can service or rebuild one of the myriad different types of early automatics is difficult. I had a lot of trouble finding a shop to rebuild the transmission in my ’56 Cadillac, and that was 30 years ago. I suppose that the promise of the Buick’s transmission has been realized with the arrival of electric vehicles, which have seamless power delivery.
Aaron, thanks for yet another highly informative article. I find it amazing the GM allowed their respective divisions so much leeway in their transmission designs. The transmission featured here seems like a real Rube Goldberg device. It is no surprise that GM mandated that all their cars share the THM series.
I have long suspected that transmission design has been part of what has driven collector interest in GM cars of this era. Buick, Cadillac and Chevrolet have been quite popular, with Pontiac and Oldsmobile much less so. I think the inherent problems of the Roto Hydramatic is a factor. Old original Oldsmobiles and low-end big Pontiacs are virtually absent from the collector/cruise-in circuit. These and the 4 speed H-M (and the PG, of course) have been relatively easy to keep on the road.
Thanks for this; I am always a bit enthralled with your detailed explanations of these Buick automatics. It’s been very enlightening.
I vividly remember riding in Buicks of this vintage and noticing the utter lack of a shift. It made them feel so creamy.
Of course the fascinating thing is how GM started with the two polar opposites of automatics, with the very mechanical-feeling four-speed HM without a torque converter and the Dynaflow/PG. And of course eventually the two concepts sort-of merged with the THM series.