Popular in Europe since the early ’30s, sunroofs didn’t really catch on in the U.S. until the 1970s, but that didn’t mean automakers didn’t periodically try. Way back in 1939, the senior General Motors marques — Pontiac, Oldsmobile, Buick, LaSalle, and Cadillac — introduced a surprisingly modern sliding sunroof option called the Sunshine Turret Top roof. It survived for only three years and is extremely rare today.
Unveiled in the fall of 1938 as an option for certain 1939 GM models, the Sunshine Turret Top wasn’t even close to being the world’s first sliding sunroof. As Tom Halter has previously chronicled, the Pytchley Roof was introduced in the UK in the 1920s, and by the early ’30s, “sunshine roofs” were common on even fairly cheap British and European cars. However, sunshine roofs hadn’t really caught on in the U.S. They were occasionally added by coachbuilders or by special order, sometimes for commercial customers like taxicab companies. Every so often, a private customer might demand one — I found a July 1934 Automotive News item about a Buick Series 90 that had been special-ordered with a sunshine roof for a buyer in Pasadena, California — but that was the exception rather than the rule.
The GM Sunshine Turret Top roof was developed by the Ternstedt Manufacturing Co., a division of Fisher Body. Alvar K. Ternstedt had developed the first practical crank-operated window regulator mechanism around 1911 and then started a Detroit company to manufacture it, financed by the Fisher Brothers. Fisher bought out the company after Ternstedt’s death in 1920, and it survived as a Fisher Body division after GM acquired Fisher Body in 1926. In the late ’30s, Ternstedt engineer Emory Glenn Simpson designed the top mechanism for the Sunshine Turret Top, while his colleagues James H. Wernig and Gustave Chutorash designed the latch mechanism.
Why was it called “Turret Top”? At the time, all-steel automotive bodies were still fairly novel in the U.S.; until the mid-1930s, many American cars still used wood bracing under their metal panels to prevent vibration and drumming. It wasn’t until 1935 that GM closed bodies adopted a welded steel roof structure with a one-piece steel roof stamping and channel steel rather than wooden top bows, an arrangement that GM marketing proudly christened the “Unisteel Turret Top.” When the sunshine roof was added four years later, GM called it the “Sunshine Turret Top roof” to emphasize that the sliding panel “in no way weakens the top construction or diminishes the safety feature of the turret top.”
Simpson, Wernig, and Chutorash were able to patent their design for the Sunshine Turret Top roof (as US2245832 and US2201330), although they emphasized that sunroofs themselves were not a new idea. “Sliding tops are in general old and the present invention relates to improvements in the mechanism,” Wernig and Chutorash noted.
If you’ve never looked closely at the mechanism for a sliding sunroof, you might assume there’s nothing very technically challenging about creating a movable roof panel. The trick with this type of sunroof is enabling the panel to sit flush with the roof opening (and seal adequately) when closed, and yet disappear almost completely into the car when open. The GM approach was very similar to a lot of modern sunroofs: The top panel (which GM called the lid) had metal extensions at each corner attached to small trunnions, which slid in U-shaped metal tracks with rubber bumpers at each end. Each trunnion was covered with felt to reduce noise. At the back, concealed within the roof structure, was a spring-loaded ramp and roller arrangement that allowed the lid to roll more easily and applied an upward force on the panel to keep it from rattling and to aid closing.
Unlike modern sunroofs, which typically use electric motors to move the lid, the Sunshine Turret Top system was completely manual, although its actual mechanism was generally similar to its later descendants. Its latches were operated by a T-shaped handle, which could secure the lid in any position, aided by the upward spring-loading of the rollers. When closing the sliding panel completely, the latches applied leverage to force the lid upward into its opening. The Oldsmobile shop manual explained the latch system like this:
As the operating handle to be seen inside the body is turned to the locked position, it actuates two bars that are similar in appearance to the rear trunk compartment lid arms. At the end of these arms is the above referred to small levers. These two levers hook around small metal posts located in the extreme forward end of the track, and force the lid fully closed as the handle is turned. The action of this lever takes place at the same instant the lid raises on the ramp at the rear edge. … A small spring loaded lever, also located at each end of the locking handle bar mechanism automatically prevents the lid from sliding forward or backward once moved and locked to a desired position. This is accomplished by forcing the lever into notches in the “U” shaped tracks. The control handle releases the small levers from the notches when the lid is moved.
How did the retractable panel actually seal? In plan view, the lid and its opening were tapered so that they were slightly narrower at the front than the back. The opening had a weather-sealing strip all the way around, while the lid had a felt-lined molding around three of its four sides. When the latches closed, the levers would wedge the lid against the sides of the opening, compressing the seals to keep dust and water out. The back edge of the lid had a sponge rubber seal to keep water out of the top compartment with the roof behind it.
Even with the top firmly wedged in place, the edge seal wasn’t completely watertight. So, like modern sliding sunroofs, GM provided a metal gutter around the opening, with a drainage hole at each corner leading to metal drainage tubes concealed in each roof pillar. As long as the drainage tubes were clear and the car was reasonably level, any water that bypassed the edge seal was supposed to be caught by the gutter and run out through the drainage tubes to the ground. Although I don’t think GM made any specific maintenance recommendations, it was very important to keep the drainage tubes clear, or else rainwater could accumulate behind the lid and leak into the cabin. (This is still true of modern power sunroofs, as I discovered the hard way some years ago!)
All things considered, the Sunshine Turret Top was surprisingly inexpensive. On a Pontiac, Oldsmobile, Buick, LaSalle, or Cadillac Series 61, it listed for $37.50 — more than you’d pay for a fresh-air heater in those days, but less than a radio. The sunroof was also available on the bigger Cadillac Fleetwood Sixty Special, where it cost a heftier $85.00. (Cadillac suggested that it was a good option for buyers who expressed interest in a convertible version of the Sixty Special, which Cadillac didn’t offer.)
The Sunshine Turret Top was available only on two- and four-door five-passenger sedans, and except for the Cadillac Sixty Special, it was offered only on B-body cars. Thus, Oldsmobile buyers could have a sunshine roof on a mid-level Olds Series 70 or Series 80, but not the fancier Series 90, while Buick offered the sunroof only on the Special and Century, not the bigger Roadmaster or Limited.
Production ended up being very limited. I wasn’t able to find any installation figures for Buick or for Pontiac (which didn’t introduce the option until later in the 1939 model year than the other divisions), but it appears that the sunshine roof was most popular in the 1939 LaSalle line. Here are the totals I was able to find:
| Model | 1939 | 1940 | 1941 |
|---|---|---|---|
| Buick Special Model 48 two-door sedan | ? | ? | ? |
| Buick Special Model 41 four-door sedan | ? | ? | ? |
| Buick Century Model 61 four-door sedan | ? | ? | ? |
| Cadillac Series 61 four-door sedan | 43 | N/O | N/O |
| Cadillac Sixty Special four-door sedan | 280 | 233 | 185 |
| LaSalle Series 50 two-door sedan | 23 | 9 | N/O |
| LaSalle Series 50 four-door sedan | 404 | 140 | N/O |
| Oldsmobile Series 70 two-door sedan | 17 | ? | ? |
| Oldsmobile Series 70 four-door sedan | 82 | ? | ? |
| Oldsmobile Series 80 two-door sedan | 7 | ? | ? |
| Oldsmobile Series 80 four-door sedan | 85 | ? | ? |
| Pontiac Series 28 DeLuxe 8 two-door sedan | ? | ? | ? |
| Pontiac Series 28 DeLuxe 8 four-door sedan | ? | ? | ? |
Some Sunshine Turret Top cars (including 24 of the 1939 LaSalle four-door sedans) were exports built in CKD form for assembly overseas, and were not originally sold in the U.S.
It’s not clear if any 1940 or later Pontiac, Oldsmobile, or Buick cars were actually built with the sunshine roof, although it was still a cataloged option in 1940. The Fisher Body service and assembly manual suggests that the sunroof wasn’t available with the new-for-1940 “Torpedo” bodies, although it may still have been available on the standard bodies, which were mostly carryover from 1939. Cadillac no longer offered the Sunshine Turret Top roof on the Series 61 after 1939, but it was still available on the LaSalle Series 50 in 1940 and on the Cadillac Sixty Special in 1940 and 1941. I didn’t see any indication of it being available in the shortened 1942 model year, and the option didn’t return after World War 2.
Why didn’t the sunshine roof sell better? It wasn’t outrageously priced, and while it could leak, especially if the drainage tubes got clogged, I don’t think that was the main problem. GM may have erred in not offering the option first in the senior C-body models, to build some buzz; the sunroof appears to have appealed more strongly to LaSalle and Cadillac buyers than to middle-class customers looking at a Buick Special or Olds 76 sedan. Also, while sunroof-equipped sedans are common today, I don’t think the five-passenger closed touring sedan was exactly considered the height of glamour in 1939.
The bigger problem for Fisher Body may have been that the Sunshine Turret Top wasn’t priced high ENOUGH considering how much of a hassle it was to install. The Oldsmobile shop manual explained:
The special top construction differs considerably. For example, the lid when pushed open (back), slides into a compartment in the top assembly. The regular top stamping acts as an upper cover for this compartment, whereas an inner metal stamping serves as a lower cover and floor. The inner panel extends back to approximately even with the edge of the rear seat back cushion. This panel is covered with the headlining material. With the exception of a couple of headlining listing rods at the extreme rear of the top, all cross bows have been eliminated. The dome light too, has been moved to a position just ahead of the rear window opening.
In addition to these significant structural changes, sunshine roof cars also required an extra set of assembly procedures to check that the roof lid could slide and close easily. Making those changes on the regular production line was a big headache for a low-volume option. I think except maybe at the very beginning of the 1939 model year, the sunroof was mostly a special-order item, and the manufacturing people probably weren’t too happy to see one come through.
When U.S. automakers began offering sunroofs again in the 1960s, the feature was initially offered on personal luxury models like the Ford Thunderbird and later the Mercury Cougar, Lincoln Continental Mark III, and Cadillac Eldorado, whose affluent customers were more likely to find the novelty enticing. Domestic automakers of the ’60s and ’70s also tended to outsource sunroof installation to companies like the American Sunroof Corporation, which wasn’t any cheaper for customers, but was less of a logistical hassle for American-style mass production.
Since the Sunshine Turret Top was not common even when new, survivors are rare. If you get close enough to see the trim plate, you can identify an original sunshine top car by the “A” suffix at the end of the body style number. For instance, the trim plate of the 1941 Cadillac shown here has a style number 41-6019SA, which means a 1941 Series 60 five-passenger touring sedan (Special) with sunshine roof.
Cadillac reintroduced a sunroof option during the 1969 model year. At first, it was almost as rare as it had been in the ’40s, but by 1979, sunroofs were being installed in hundreds of thousands of domestic cars, including about 7.5 percent of all Cadillacs and almost 17 percent of Eldorados. So, the old Sunshine Turret Top was just way ahead of its time.
Related Reading
Curbside Tech: History of the Sliding Sunroof and Moonroof, Part 1 (by Tom Halter)
Curbside Tech: History of the Sliding Sunroof and Moonroof, Part 2 – A New Moon(roof) (by Tom Halter)
I’d quite forgotten about these, although seeing the ads does ring a somewhat distant bell of having encountered them somewhere along the line. I used to spend days at the main Baltimore City Library perusing old magazines having hooked school. I suspect I saw some of these old ads.
I loved the sunroof on my Peugeot 404, and had it open almost constantly, given the So Cal weather.
Ah the Enoch Pratt, one of the best in the country. They had huge collections of old magazines, while the old Towson library behind Stebbins had few to none, but I liked to read the Consumer Reports.
Someone gave my folks a bunch to National Geos going back to the ’30s and up to mid-60s so I cut out all the car ads and put them in a notebook. All thrown out by my father’s new 2nd wife when I went to college…grrr. Most ’30s ads were B&W but the later ’50s ads were quite colorful. My favorites were the ’57 DeSotos showing off their 2 tones and big fins! And lot’s of Cad, Lincolns and T-bird ads in the ’60s.
I’ve never been in person, but Enoch Pratt helped me get some material on the Chrysler disc brakes last year. They still have a LOT of automotive stuff.
Based on hazy, magical memories of road trips as a kid, it’s fun to imagine what it must have felt like in 1939 to make the long drive down to Florida from the north in December, waking up perhaps in a motor hotel in Jacksonville one morning, and continuing south with your ‘Sunshine Turret Top’ open in warm sunshine for the first time.
Oh Aaron, you’ve done your very best, as ever, but I’ll confess to being a bit thick on tech things, and in the case of sliding sunrife, I have always considered them a dark mystery. I will read this again when my brain is less cranky, but that whole flush-drop-down-and-back thing has always confounded me, let alone the sealing of the whole shebang.
Seems VW et al has the same issue, btw, as it seems every vehicle they make, from a Bentley to a Polo, leaks from the sunroof after a bit.
Almost as an aside, what a super-handsome crop of cars GM turned out in this small window of time, with or without a hole in their heads.
Generally, this kind of internal-retraction sunroof leaks for one of two reasons. The most common is that the little drainage tubes get clogged with dust and dirt during a long, dry summer, so that when the monsoon season hits, water can’t drain around the sides of the thing and backs up. This can be mitigated by periodically clearing out the tubes with a long length of pipe cleaner, which mechanics and dealer service bays will do for a nominal charge, but it’s not necessarily on the maintenance schedule and people don’t know or think to do it.
The other scenario, which put me off these things for life, is if the car is parked outside at some kind of a funny angle — sloped driveway, side of a banked road, that sort of thing — during a heavy rain. In that case, some of the incoming water will miss the gutter and end up in the cabin or in some part of the roof structure where it’s not supposed to go. Modern glass sunroofs usually have a separate sliding panel in the headliner below the glass, so you don’t have to get boiled by the sun if you don’t want to be, so the water overflow will hit that and run backwards into the well where the lid is supposed to sit when the roof is open. This is a basic design flaw, and there’s no fixing it other than to park in a garage or on a level street if it’s raining very hard.
Pop-up sunroofs (that is, the kind that only pop up — some sliding roofs can stick their noses in the air like trained seals) generally don’t have this over-cunning internal drainage system, so they rely on cranking the lid down against a lip seal to keep the rain out. There, the leading cause of leaks is worn seals, either because the gasket gets torn or because the adhesive holding it down dries out and cracks.
I’m another who has a really dim memory of reading about these, but had completely forgotten about them.
I wonder if a motoring public freshly spoiled by leak-free 1-piece steel roofs was not excited by this invitation to leakage. And on the other end, this was the heyday of the convertible sedan, which was a way to get sunshine without compromise.
I remember sunroofs coming back as convertibles went away around 1970 or so, but I’m not sure I ever knew anyone who owned one.
Convertible sedans did sell better than sunshine roofs, but they were 0.25 percent of the U.S. market in 1939, which meant 7,167 cars across the entire U.S. industry. The “heyday” of the convertible sedan in terms of sales volume was 1937, when a whopping 14,341 were sold in the U.S. and Canada — a niche market, to be sure.
I think the problem was primarily that GM offered the roof on the wrong models. The typical Buick Special sedan buyer was often the family that was stretching the budget a bit to be able to say they drove a Buick; asking them to pay extra for this unnecessary feature was a lot. If GM had introduced it on the Sixty Special, Roadmaster, and Limited, publicized it a bit more, and then extended it to the B-body cars, they might have had better luck.
I always wondered why they waited till the hole was closed, then opened it again a few years later. The Euro divisions of GM and Chrysler simply inserted folding cloth or sliders into the hole. Here are a couple of ’35 British Dodges.
US Chrysler closed the hole the simple way in ’36 by welding in a panel, then did it the GM way in ’37. Chrysler also offered re-opened sunroofs in ’39, but very few were bought.
In the late 50’s and early 60’s British cars were quite common all through New England so I became enamored of the steel sliding roofs .
The raising up part is typically very simple, some ramps that must needs be kept lubricated by a special “dustless” grease, I use WWII surplus Lubriplate rifle grease, I don’t know how they make it slippery yet not attractive to dust but is it so .
I find using weed whacker line (plastic, very strong and extremely flexible) to clean the drains he way to go .
The front drains are easy to see / access with the roof open, the rear drains exit under the car so one has to work from below .
My second vehicle and first car was a 1960 VW #117 with the sliding canvas sunshine roof, it was marvelous and never leaked .
Once in a blue moon I’ll find a 1970’s American car with sunroof, a shame to see them scrapped .
-Nate
A can of air for dusting electronics cleans the lines well for me. Fill the line with as much water as will go in then insert the air tube and make a sort of seal with a finger. The weight of the water propelled by the air does the work.
Absolutely fascinating post Aaron, thank you! My first sliding sunroof experience was my grandparents’ ’73 Volvo 164E. Once I was buying cars, I eventually bought an ’86 Ford Sierra Ghia with sliding glass sunroof. I loved it and since then have made a point of buying cars with sliding sunroofs where possible. In fact I like sliding sunroofs so much that when I owned a sunroofless ’94 Nissan Skyline, I bought a Skyline roof cut with factory sunroof and had it fitted to my Skyline – the engineer drilled out all the spot welds on both panels, swapped them welded it back in and bolted in all the mechanism etc from below. Nowadays both our Peugeots have fixed panoramic glass roofs, but I still get my sliding roof fix via my ’89 Ford Sierra.