From 1953 to 1978, British automaker Rolls-Royce manufactured its own versions of the General Motors Hydra-Matic transmission for use in Rolls-Royce and Bentley luxury cars. One version was very similar to the Hydra-Matic used in American cars and trucks, but Rolls-Royce later created an improved aluminum-case version with modifications to provide smoother shifting. This version was offered in some versions of the Rolls-Royce Silver Shadow I and Bentley T Series from 1966 to 1969. The older version remained in use in the big Phantom V and Phantom VI limousines until 1978.
Although the Hydra-Matic transmission was first used by Oldsmobile and Cadillac, the final user was not a GM division, but Rolls-Royce, which used its own license-built versions of this highly successful GM transmission from 1953 to 1978. This included an unusual, short-lived variation for the early Rolls-Royce Silver Shadow and Bentley T-Series — the last iteration of the original Hydra-Matic transmission. In this installment of Ate Up With Motor, we take a look at the upper-crust British career of this venerable American automatic transmission.
IMPORTANT AUTHOR’S NOTE
On an article like this, it bears repeating in boldface type: I CANNOT to tell you how to fix any of these transmissions, I DO NOT sell (or buy) parts for them, and I can’t help you find parts! If you have transmission maintenance, repair, or troubleshooting questions, I strongly recommend that you seek out the factory service manuals and/or consult a transmission specialist familiar with older automatics. (I am NOT a mechanic and am NOT qualified to give troubleshooting or repair advice.)
THE HYDRA-MATIC COMES TO CREWE
As we recounted in our original Hydra-Matic article, users of this revolutionary early automatic transmission included not only GM divisions, but also a surprising number of other automotive marques, including Lincoln, Kaiser, Nash, and Hudson. Most non-GM automakers purchased complete transmissions from GM’s Detroit Transmission Division (which became Hydra-Matic Division in October 1963), even using the Hydra-Matic name in their marketing and even badging. The exception was Rolls-Royce, which manufactured its own versions of the Hydra-Matic transmission under license in Crewe, England, for use in Rolls-Royce and Bentley passenger cars. (Rolls-Royce owned Bentley Motors from 1931 until 1998.)
Both before and after World War II, Rolls-Royce chief engineer W.A. Robotham (abbreviated “Rm” in internal memoranda) had taken a keen interest in the latest developments in American automotive engineering. Although that was a somewhat controversial point within the company, Rolls-Royce routinely purchased examples of other manufacturers’ cars for testing and evaluation, including American models from Buick or Cadillac, and Robotham visited the U.S. in 1932 to examine the latest automotive developments firsthand. During that visit, he saw some of the early work on the Military Transmission project, which subsequently evolved into the Automatic Safety Transmission and the original Hydra-Matic.
Although wartime activity was the major priority for Rolls-Royce from 1939 to 1945, some passenger car development work continued during the war, including early experiments with automatic transmission. In 1944, one experimental car was fitted with a Brockhouse Turbo-Transmitter, a torque converter transmission later offered in the limited-production Invicta Black Prince, while in 1945, a Hydra-Matic transmission was apparently installed in “Big Bertha,” an eight-cylinder Silver Wraith limousine. (There may have been earlier Hydra-Matic tests as well; journalist Laurence Pomeroy, later technical editor of The Motor, reportedly recalled driving a Rolls-Royce so equipped during the war.) Robotham and design chief Ivan Evernden found the postwar Hydra-Matic greatly improved from early examples (thanks in part to extensive wartime use in light tanks and other military vehicles). It was now a reasonably well-sorted transmission that could be adapted to the needs of Rolls-Royce and Bentley without too much difficulty.
In March 1946, Robotham flew to Detroit to talk to GM executives, including O.E. Hunt, vice president of the corporate Engineering Staff, and John F. (Jack) Gordon), general manager of Cadillac, whom he had met during his earlier visit to the U.S. From these meetings, Robotham learned that the Detroit Transmission Division was preparing to greatly increase production capacity, anticipating increased demand for Hydra-Matic internally and the possibility of outside sales. However, Robotham confounded nearly everyone he spoke to at GM by insisting that he didn’t simply want to buy Hydra-Matic transmissions; he wanted Rolls-Royce to license the manufacturing rights.
With the help of Jack Gordon, Robotham arranged a meeting with GM president Charles E. Wilson. Wilson was as puzzled as his subordinates had been about the economic logic of Robotham’s proposal — the 5,000-unit annual production estimate Robotham cited, though extravagantly optimistic for Rolls-Royce (whose typical annual passenger car production over the next 25–30 years, including Bentley cars, would be roughly half that), was very small beer by GM standards. Nonetheless, by the end of the meeting, they had reached an agreement, at least in principle.
Robotham’s account doesn’t explain why he was so emphatic about building Hydra-Matic rather than buying complete transmissions, but we’ll hazard several guesses. Company pride likely had something to do with it, but it may also have been significant that his trip to Detroit came less than a year after V-E Day. After six years of a conflict during which many thousands of tons of supplies and matériel had ended up at the bottom of the Atlantic Ocean, it’s understandable that Rolls-Royce might have been uneasy about relying too much on an overseas supplier for an essential subsystem, and there were at that time almost no local alternatives if the supply from the U.S. were to be cut off for any reason. (We assume the Brockhouse torque converter unit was judged unsatisfactory; its subsequent automotive career with Invicta was brief and unhappy.) Beyond that, Great Britain’s postwar Labour government was putting considerable pressure on industry to increase exports, and the cost of importing transmissions would likely have been high, even if GM’s unit price was reasonable.
After his return from Detroit, Robotham’s attention shifted to other matters (he subsequently became head of the company’s new diesel engine division, ending his involvement with passenger car development), so his memoir offers no insights on why it took an additional seven years before Crewe began production of the automatic gearbox. Aside from the various practical and logistical challenges involved in any transatlantic manufacturing agreement, particularly in the era before fax machines and email, Rolls-Royce may have opted to wait for the introduction of the revised Dual-Range Hydra-Matic, launched in the U.S. in the fall of 1951, which offered a much greater degree of manual control for the driver than did earlier Hydra-Matic transmissions.
Rolls-Royce also attempted to bring the automatic gearbox up to expected Crewe standards of finish and production tolerances, a Pyrrhic effort that only added to the new transmission’s teething pains. For example, early Crewe-made transmission brake drums had a smoother surface finish than the ones made in Detroit, which turned out to cause erratic shifting (we assume by making it harder for the brake band to securely grip the drum). In most such areas, Rolls-Royce eventually conceded that it was attempting to fix things that weren’t broken, and decided that the better part of valor was to follow GM’s lead.
THE AUTOMATIC GEARBOX
Automatic became available on Rolls-Royce and Bentley export cars in 1952, initially using a batch of imported Detroit-built transmissions fitted with Rolls-Royce driveshafts and a tail extension incorporating the power takeoff shaft needed to drive the mechanical brake servo (a curious device Rolls-Royce had used since 1924). Rolls-Royce announced the automatic as an option for British-market Rolls-Royce and Bentley models in the fall of 1953, priced at £99 3s 4d with purchase tax (equivalent to about $278 at the contemporary exchange rate), although few production cars received Crewe-built automatics before the end of the year.
The automatic gearbox became standard on the new Rolls-Royce Silver Cloud and Bentley S Type in 1955. Rolls-Royce also sold some transmissions to Armstrong Siddeley, which offered the automatic as an option on the Sapphire 346 from 1954 to 1958, and later to BMC for use in the Vanden Plas Princess 4-litre (though not the later Princess 4-litre R, which used a Borg-Warner automatic behind its 3,909 cc (239 cu. in.) Rolls-Royce FB60 six). The Jensen 541S, which used the big 3,993 cc (244 cu. in.) Austin six, also offered the Rolls-Royce automatic, although later Jensen models with Chrysler V-8 engines adopted the Chrysler TorqueFlite transmission instead.
Although Rolls-Royce made no secret of the new automatic’s Detroit parentage, they sternly advised the press to describe the transmission as “the Automatic Gearbox” rather than as “Hydra-Matic,” which was (and remains) a registered trademark of General Motors. (We assume the license agreement did not include the rights to use the Hydra-Matic name on transmissions not built by GM.) Nonetheless, the Rolls-Royce transmission was very similar to its American-made cousin, even sharing the same ratios: 3.82:1 in first, 2.63:1 in second, 1.45:1 in third, 1.00:1 in fourth, and -4.30:1 in reverse.
Like the Detroit-built Dual-Range Hydra-Matic, the Rolls-Royce automatic gearbox had three driving ranges, which Rolls-Royce labeled “4,” “3,” and “2.” “4” range started in first gear and used all four forward speeds; “3” range locked out fourth gear until high speeds; and “2” kept the transmission in second gear in most conditions, as well as allowing second-gear starts. When the first RHD automatic cars were unveiled at the Motor Exhibition at Earls Court in London in October 1953, some credulous British journalists assumed these controls were a Rolls-Royce exclusive, apparently unaware that the Hydra-Matic transmissions used in some quite ordinary GM cars and trucks now offered the same features.
Crewe-built automatic gearboxes had revised hydraulic controls that prevented the transmission from automatically upshifting in “2” range (in L, Dual-Range Hydra-Matic would eventually shift to fourth gear to prevent over-revving) and eliminated the provision for part-throttle kickdown. You could still trigger a downshift by pushing the accelerator all the way to the floor, but because kickdown changes exacerbated the transmission’s tendency to shift with a thump, Rolls-Royce recommended selecting the “3” or “2” range to execute a 4–3 or 3–2 downshift, which was smoother and often quicker. Crewe-built transmissions also had a tail extension incorporating the power takeoff for the brake servo and the oil pump for the hydraulic ride control unit used on some models.
Like the contemporary Hydra-Matic transmission, the Rolls-Royce automatic gearbox had many virtues. Low-speed “creep” was minimal, and the split torque arrangement in third and fourth gears (in essence, a partial mechanical lockup) reduced the effects of slippage in the fluid coupling. There was no way to manually control the 1–2 shift or to hold first gear, but you could choose whether to start in first or second, and the “2” and “3” ranges provided useful control of the intermediate gears. It was possible to shift quickly between “2” and reverse to rock the drive wheels free of mud or snow, and the use of front and rear oil pumps allowed push-starting in a pinch. With proper maintenance, the automatic gearbox was also reasonably robust.
To our knowledge, Rolls-Royce didn’t offer comparable manual and automatic cars for back-to-back independent road tests during the brief period in which the automatic was still an optional feature, but automatic-equipped models had respectable performance for the period. With its dual oil pumps, the automatic undoubtedly consumed significantly more power than a manual gearbox did, and overall gearing wasn’t ideal for unrestricted European roads, but the low (high numerical) first gear and modest slippage in the higher gears provided some compensation.
It probably helped that the engines with which the Rolls-Royce and Bentley transmission was paired were not too different from those with which the American-made Hydra-Matic had been paired: initially, a big F-head (intake over exhaust) inline six, replaced in 1959 by the new 6,230 cc (380 cu. in.) L410 V-8 — an all-aluminum OHV engine with oversquare dimensions, wedge combustion chambers, and hydraulic valve lifters, like the latest Detroit V-8s. (Before we inadvertently start any arguments, let us hasten to note that the L410 was not a copy of any American V-8 engine. However Rolls-Royce did adopt a hydraulic valve lifter design developed by Chrysler, again opting to manufacture the components in Crewe.)
As for refinement, by the fifties, single-coupling Hydra-Matic transmissions were reasonably civilized in gentle driving, especially with a little finesse in throttle application, but shifts were noticeably firmer than rival torque converter automatics, something that became more pronounced if the bands and throttle valve linkage weren’t properly adjusted. Since automatic transmission was still uncommon outside the U.S., British and European buyers had few points of comparison, but the jerkiness had become a sore point for American customers.
To keep pace with the rapid-evolving U.S. market, the Detroit Transmission Division introduced the thoroughly updated Controlled Coupling Hydra-Matic, which superseded the Dual-Range Hydra-Matic in most passenger car applications for 1956. Controlled Coupling Hydra-Matic (discussed more fully in the the second part of our history of early GM automatics) replaced the older transmission’s multi-disc front clutch with a “dump-and-fill” second fluid coupling and used sprag clutches instead of brake bands in most normal driving. The redesigned transmission was significantly smoother, but also even more complex and expensive than before, which appears to have been a commercial miscalculation. Most non-GM customers shied away, opting instead for cheaper automatics from rivals like Borg-Warner.
Had Rolls-Royce been simply buying Hydra-Matic off the shelf, they would have had a number of options at that juncture — continue with the single-coupling Hydra-Matic (which remained in production for light truck use into the early sixties), switch to the dual-coupling Hydra-Matic, or consider new alternatives like the Chrysler TorqueFlite — but having only recently established production in Crewe meant that Rolls-Royce were committed to the existing transmission, at least for the moment. (Interestingly, in 1957, a V-8 prototype was fitted with a Buick Dynaflow torque converter transmission, perhaps for evaluation purposes. It was replaced with a four-speed Rolls-Royce automatic about two years later.)
THE SILVER SHADOW AND THE GM 400
In the autumn of 1965, Rolls-Royce unveiled two all-new models to succeed the Silver Cloud III and Bentley S Series: the Rolls-Royce Silver Shadow and closely related Bentley T Series. The new cars retained the 6,230 cc (380 cu. in.) aluminum V-8, but were otherwise thoroughly updated, now using monocoque construction (with front and rear subframes), fully independent suspension with hydraulic self-leveling (using technology licensed from Citroën), and four-wheel disc brakes.
Left-hand-drive cars also had a new transmission: the latest GM Turbo Hydra-Matic (a.k.a. TH400), shared with some contemporary full-size General Motors cars. Although Rolls-Royce and Bentley units had serial numbers beginning with “RR” (and, according to some sources, tighter production tolerances than the GM norm), these three-speed torque converter transmissions were manufactured by Hydra-Matic Division rather than in Crewe. Rolls-Royce literature generally describes this transmission as “GM 400,” but the factory workshop manuals also use the Turbo Hydra-Matic name.
Early right-hand-drive Silver Shadows and T Series Bentleys did not have the GM 400 transmission, instead continuing with the fluid coupling four-speed automatic. It would be natural to assume that this was a carryover of the transmission from the last Silver Ghost III and Bentley S Series, but in fact the four-speed transmission had undergone some substantial changes, creating the final new variation of the original single-coupling Hydra-Matic.
The first major change was a new case. Where earlier Hydra-Matic transmissions were primarily cast iron, the new unit had a cast aluminum case, including the bell housing, tail extension, and some internal castings. (Crewe-built transmissions already had an aluminum side cover and sump.) We haven’t found any figures suggesting what weight savings this change achieved, but we would guess something on the order of 60 to 70 lb (27 to 32 kg), offset somewhat by some of the other internal revisions.
A second important revision, shared with Rolls-Royce and Bentley GM 400 transmissions, was an electric shift actuator system, providing fingertip control of the various driving ranges. The actuator was an external add-on, mounted on the side of the tail extension. It used a double-wound electric motor to move the transmission selector shaft lever, with a solenoid-operated brake to hold the actuator securely in place after each selection. Apparently having noted the troublesome results of earlier American attempts at electric shift control, Rolls-Royce added an access port in the transmission tunnel through which a small tommy bar (described in the workshop manual as the “Get-You-Home Bar”) could be inserted to manually operate the selector level if the electrical system failed. The electric shift actuator also had a new R-N-4-3-2 shift pattern; on earlier cars with the four-speed automatic, reverse was below “2” at the bottom of the pattern.
The third and most significant change was in the transmission’s internal layout, which was revised to incorporate one of the changes GM had made for the Controlled Coupling Hydra-Matic: a one-way sprag clutch that took over the role of the rear brake band in “4” and “3” ranges. The effects of these changes are explained in more detail in the sidebar below, but the object was to smooth out the transmission’s occasionally harsh shifts.
PAST ITS PRIME
While less elaborate than the dual-coupling Hydra-Matic transmission (which GM had just recently retired), the revised Rolls-Royce four-speed automatic was noticeably smoother in operation than before. Contemporary British road tests of the early RHD Silver Shadow found shifts barely perceptible most of the time, although downshifts into second gear could still elicit the occasional jerk. As before, it was better to avoid kickdown and use the range selectors to shift down when needed, which the electrical selector made very easy.
The only really glaring problem with the updated transmission was that it was still clearly inferior to the new Turbo Hydra-Matic used in LHD cars. The GM 400 transmission’s torque converter (initially equipped with a variable-pitch stator like the ones used on 1965–1967 Buick, Cadillac, and Oldsmobile units) obviated the need for the older four-speed’s high numerical first and reverse gears — starting ratio at torque converter stall could be up to 5:1 in first and 4:1 in reverse, enough that the first prototype fitted with the new transmission snapped a halfshaft on a full-throttle start. The use of sprag clutches for both of the reaction members of the compound Simpson gearset also allowed most shifts up or down to be effected by engaging and disengaging a single multi-disc clutch, eliminating most of the older transmission’s mechanical folderol.
More importantly, Turbo Hydra-Matic had a new and considerably more advanced control system. Unlike the older Hydra-Matic transmission, which measured load using a throttle valve controlled by a series of rods and levers, Turbo Hydra-Matic used a vacuum modulation system that could vary both shift points and operating pressures based on engine vacuum, providing crisp, decisive shifts under hard throttle and nearly seamless changes in gentler driving. Units tuned for high-performance applications, like the M40 transmissions used in some GM muscle cars, could be as harsh and jerky as an early four-speed Hydra-Matic on its worst days, but Turbo Hydra-Matic was an adroit partner for a torquey, mildly tuned six or V-8, seeming to nearly always make the right moves.
Against such formidable opposition, the older four-speed automatic, however improved, was simply outclassed. Consequently, the aluminum-case four-speed gearbox was short-lived. RHD export cars switched to Turbo Hydra-Matic in 1968, and home-market Silver Shadow and T Series cars had adopted the GM 400 transmission by 1969. (Factory literature marks the change based on chassis numbers rather than model years or delivery dates.)
Why would Rolls-Royce spend the money necessary to update the four-speed automatic, only to quickly phase it out? Our guess is that that wasn’t the original plan. The Silver Shadow had a lengthy gestation; early development began in February 1954 under the codename “Tibet,” with tests of prototype cars commencing in 1958. After a number of false starts, including an abortive Bentley project codenamed “Burma,” Rolls-Royce consolidated its various development efforts into the S2500Y (or SY) program, which became the Silver Shadow and Bentley T Series. It was not until after SY development began in mid-1963 that GM introduced Turbo Hydra-Matic, which was first offered on some 1964 Buick and Cadillac models. Prior to that point, therefore, it seems likely that Rolls-Royce engineers assumed that the new models would retain the four-speed automatic indefinitely, and that the revisions to the older transmission were made on that basis.
However, Turbo Hydra-Matic was plainly superior to the four-speed automatic in every respect. Moreover, the availability of Turbo Hydra-Matic on American luxury cars would further elevate buyer expectations in a crucial export market. Rolls-Royce therefore decided that all LHD export models would have the GM 400, which would eventually become standard line-wide. It’s not clear why the newer transmission wasn’t offered across the board at launch; it’s unlikely that Hydra-Matic Division would have had any difficulty supplying the modest number of additional transmissions. Our best guess is that enough work had already been done on revising the four-speed that Rolls-Royce wanted to recoup some of those costs.
Neither the aluminum-case four-speed nor the GM 400 made its way to the big Rolls-Royce Phantom V, which dated back to September 1959 and was more closely related to the older Silver Cloud II than to the Silver Shadow. Made in very limited numbers by H.J. Mulliner & Co. or Park Ward (which merged in 1961 to become a Rolls-Royce division), the Phantom V was built as a traditional rolling chassis — to facilitate custom bodywork — and still retained a live rear axle, drum brakes, and the older iron-case four-speed automatic through the end of production in 1968.
The same was true of the Phantom VI, which succeeded the Phantom V in April 1968. Surprisingly, the reason for keeping the old transmission appears to have been brakes. Unlike the Silver Shadow, the Phantom still used drum brakes — which Rolls-Royce insisted were quieter than discs — along with the old transmission-driven mechanical brake servo, whose power takeoff shaft was incorporated into the tail extension of the iron-case four-speed gearbox. The aluminum-case four-speed and Rolls-Royce GM 400 gearboxes had no provision for the servo, since they mounted the electrical shift actuator mechanism on the side of the tail extension in roughly the same place. Given the limited production of the large formal cars, we assume it was more expedient to simply continue using the earlier transmission rather than adapt the old tail extension to the newer gearboxes. (The formal cars, which were normally chauffeur-driven, also initially forewent the electrical shift actuator.)
This meant that the 1952-vintage four-speed automatic continued in limited use well into the seventies. How long it actually remained in production is less clear. We assume that Crewe would have needed to continue producing parts and spares for the earlier transmission for some years after the introduction of the Silver Shadow and Bentley T Series, for the service and repair of older cars, so assembling the modest number of complete transmissions needed for the Phantom V and VI would probably not have been a great problem. It’s also conceivable that Rolls-Royce retained a small stockpile of the earlier transmissions to draw upon for the Phantom VI; production of the big formal cars was never more than a few dozen units a year.
In 1976, the British Society of Motor Manufacturers and Traders (SMMT) commissioned production of a special Phantom VI for the Queen, originally intended as a Silver Jubilee gift, but not delivered until March 1978. This car adopted the long-stroke 6,750 cc (412 cu. in.) V-8 that had been standard on other Rolls-Royce and Bentley models since 1970, along with Turbo Hydra-Matic. Adopting the GM 400 transmission and its electrical shift mechanism required the deletion of the old transmission-driven brake servo, which was replaced by a more conventional dual-circuit hydraulic system similar to that of the contemporary Silver Shadow II, albeit with drum brakes; the Phantom VI never adopted discs.
The big engine, GM 400 transmission, and hydraulic brake system became standard on the Phantom VI later in the year, which finally consigned the old four-speed fluid coupling transmission to the history books. Remarkably, the elderly Dual-Range Hydra-Matic design managed to outlive all of its lineal descendants, including not only the aluminum-case Rolls-Royce automatic gearbox, but also the second-generation Controlled Coupling Hydra-Matic and the later three-speed Roto Hydra-Matic, which GM had dropped after the 1964 model year.
This means that the production lifespan of the single-coupling, four-speed Hydra-Matic family, introduced in the fall of 1939 as an option for 1940 Oldsmobiles, was a remarkable 39 years. During that time, these transmissions had found their way into almost every manner of automotive application, from passenger sedans to pickup trucks and armored fighting vehicles.
By the late seventies, the four-speed fluid coupling transmission was an anachronism, but it was also the grande dame of automatic transmissions, so it’s somehow fitting that it ended its long career powering royal limousines. Groundbreaking automotive technology rarely receives such a prestigious send-off.
NOTES ON SOURCES
For a full bibliography of Hydra-Matic sources, see our earlier Hydra-Matic articles.
Additional information on the late Rolls-Royce Hydra-Matic came from “After the Cloud—The Shadow,” Autocar 8 October 1965, reprinted in Rolls-Royce, 2nd ed., Peter Garnier and Warren Allport, compilers (London: The Hamlyn Publishing Group Limited, 1981), pp. 208–216; Warren Allport “Royal Phantom,” Autocar 1 April 1978, reprinted in ibid, pp. 252–254, and “Production change,” Autocar 26 February 1977, reprinted in ibid, p. 251; Warren Allport and Stuart Bladon, “The Ultimate in Luxury? A Unique Rolls-Royce Phantom VI,” Autocar 27 April 1972, reprinted in ibid, pp. 224–226; “Autocar road test 1835: Rolls-Royce Silver Cloud III 6,230 c.c.,” Autocar, 9 August 1963, pp. 234–238; “Autocar Road Test Number 2125: Rolls-Royce Silver Shadow 6,230 c.c.,” Autocar 30 March 1967, reprinted in Rolls-Royce, pp. 217–221; “The Autocar Road Tests No. 1510: Rolls-Royce Silver Dawn Saloon,” The Autocar 16 October 1953, reprinted in ibid, pp. 152–155; the Armstrong Siddeley Car Club, “The Armstrong Siddeley Sapphire 346,” n.d., armstrongsiddeley. org.au/ models/ sapphire-346/, accessed 4 September 2022; Martin Bennett, Bentley Corniche & Azure, 2nd ed. (Dorchester, England: Veloce Publishing, 2009); Bentley Motors Ltd., “Technical Library, 1955-1965,” Bentley Motors Ltd. Heritage website, heritage.bentleymotors. com/ en/ technical-library/ 1955-1965, last accessed 2 August 2022, and “Technical Library, 1965-1980,” Bentley Motors Ltd. Heritage website, heritage.bentleymotors. com/ en/ technical-library/ 1965-1980, last accessed 30 July 2022; BMW Group, “King Size. Rolls-Royce Phantom VI,” BMW Group Classic, n.d., www.bmwgroup-classic. com/ en/ history/ classic-heart/ classic-heart-pool/ classic-heart/ rolls-royce-phantom-6.html, accessed 2 August 2022; Malcolm Bobbitt, Rolls-Royce Silver Shadow, Bentley T-Series, Camargue & Corniche, 4th ed. (Dorchester, England: Veloce Publishing Ltd., 2016); Bill Boddy, “Earls Court Review,” Motor Sport Vol. XXVIII, No. 11 (November 1952), p. 518a; “Long Weekend with a Rolls-Royce Silver Shadow,” Motor Sport Vol. XLIV No. 5 (May 1968), pp. 404–408; and “New for 1966: The Rolls-Royce Silver Shadow and Bentley T-Series,” Motor Sport Vol. XLI, No. 11 (November 1965), pp. 996–999; Bonhams, “Past Auction: 1958 Armstrong Siddeley Star Sapphire,” Classic Driver Marketplace, 5 September 2015, www.classicdriver. com/ en/ car/ armstrong-siddeley/ star-sapphire/ 1958/ 326214, accessed 4 September 2022; Gavin Braithewaite-Smith, “Simply the Best? Profile: Rolls-Royce Silver Shadow,” Drives TODAY, 11 April 2021, drives. today/ articles/ 643/ history/ rolls-royce-silver-shadow/ gavin-braithwaite-smith.html, accessed 30 July 2022; Martin Buckley, “How the other half lived: Bentley MkVI vs Armstrong Siddeley Sapphire 346,” Classic & Sports Car 4 November 2020, www.classicandsportscar. com/ features/ how-other-half-lived-bentley-mkvi-vs-armstrong-siddeley-sapphire-346, accessed 4 September 2022, and “Bentley’s heartbeat: the first and last L-series V8s,” Classic & Sports Car 22 September 2020, www.classicandsportscar. com/ features/ bentleys-heartbeat-first-and-last-l-series-v8s, accessed 3 August 2022; David Burgess-Wise, “A good idea at the time: The Black Prince,” The Telegraph 13 October 2001, www.telegraph. co.uk/ motoring/ 4753430/ A-good-idea-at-the-time-The-Black-Prince.html, accessed 15 October 2015; Cadillac Motor Car Division of General Motors Corporation, 1955 Data Book (Detroit, Mich.: Cadillac Motor Car Division, General Motors Corporation, November 1954); Richard Calver’s Jensen website, www.richardcalver. com, last accessed 4 September 2022; David Chaundy, “Roll-Royce Built ‘Hydramatic’ Automatic Transmission,” KDA132, 15 April 2018, www.kda132. com, accessed 3 August 2022; Mike Covello, ed., Standard Catalog of Imported Cars 1946–2002, Second Edition (Iola, Wis.: Krause Publications, 2001); Detroit Transmission Division of General Motors, Detroit Transmission Division Welcomes You to the Home of Hydra-Matic (Ypsilanti, Mich.: Detroit Transmission Division of General Motors Corporation, ca 1958); Edward Eves, Rolls-Royce: 75 Years of Motoring Excellence (New York: Crescent Books, 1979); the Flying Spares website, www.flyingspares. com, last accessed 2 August 2022; Peter Garnier and Warren Allport, compilers, Rolls-Royce, 2nd ed. (London: The Hamlyn Publishing Group Limited, 1981); Bill Gavin, “The Doughty Dowager Comes of Age,” Car and Driver Vol. 11, No. 9 (March 1966), pp. 45–47; Norman Geeson, “History of Bentley R-Type B87UL,” KDA132, www.kda132. com/ history-of-bentley-r-type-b87ul/, accessed 3 August 2022; T. 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