Curbside Classic: GMC TDH-4523 Transit Bus

GM has built some great vehicles in its day, but nothing can top their buses. They literally owned the bus market from the forties through the seventies, but they earned that spot with superior technology and quality construction. One of the most brilliant and enduring examples of that is the “New Look” transit bus that came out in 1959, and revolutionized the field with advanced stress-skin aluminum construction and absolutely indestructible build quality. These buses are still on the road in transit duty fifty years after they first saw the light of day. A variation of this bus (the Classic) was still being produced by MCI until 1997. Given that this pictured bus was built about the same time as the 1978 Cadillac Eldorado in our last Curbside Classic, we have here a study in GM contrasts. Of course, even GM’s bus business eventually ended badly in its inimitable way.

I’ve been a lover of buses since way back, and I have a slew of bus books in the closet. We can’t do a proper survey of the genre here, but the GM buses tell a disproportionate share of the whole story. Let’s just say that transit (and over the road) buses were a pretty big business back in the day when there weren’t more cars than driver in the US. GM’s involvement in the industry dates back to the pre-war era, when they bought Yellow Coach company. And their involvement in dismembering LA’s superb light rail system after WWII in order to sell more buses is not a very pretty story.

But their buses were unimpeachable. The sort-of modern story begins in 1943 when Yellow was fully absorbed into GMC Truck & Coach. These post war buses were durable brutes, powered by GM’s legendary Detroit Diesel 6-71 2-stroke diesel engines. And GM Division Allison’s V-Series automatic was a revolution in itself. Try to imagine shifting a transit bus, double clutching every shift of the four speed un-synchronized transmission with a 40′ mechanical linkage! Shifts were extremely slow and arduous. The Allison was the greatest thing that ever happened to bus drivers.

The breakthrough modern bus was GM’s over-the-road coach PD 4104 from 1953. (This one was still hard at work in 2005 in Brazil). The construction of the 4104 completely broke with the traditional truck-type ladder frame, and was built more like an airplane with aluminum stressed-skin construction. It dramatically reduced weight, and made for an extremely rigid and solid structure. Buses have never been the same since. And 4104s are still desirable RV coach conversions.

The 4104 powered by the DD 6-71 and the manual transmission (not so painful for over-the road use) could get up to 12 mpg. And of course, it spawned the legendary 4105 Scenicruiser. That was specifically designed and produced for Greyhound, and curiously, unlike most of GM’s other buses, suffered from some structural problems. The complicated twin-engine (two 4-71 four cylinders) setup was also problematic, and were later rebuilt with a single 8-71V engine. But they were impressive sights in their day, and I remember some memorable trips in them.

GM’s New Look transit buses used the construction techniques that the 4104 pioneered. The benefits were manifold, but none more so than for the driver. Visibility was beyond superb; it was like sitting in a green house compared to the “submarine” predecessors. And the steering was substantially lighter because of the lower weight. Note that power steering on these was highly optional; the power came from well developed arm muscles and the leverage of a large wheel and a high (numerical) steering ratio.

The Allison VH transmission was a god-send, but a curious affair. It had all of…one speed. It was really just a torque converter with a massive amount of hydraulic effective gear range. On take-off, which was (in my case) always with full throttle, the engine spun up to full speed, and the bus would lumber away. Depending on vague factors beyond anyone’s apparent knowledge, at some speed of around 30 or 35 or so, the torque converter would be mechanically locked (with a substantial jolt), and now the engine was in direct drive. Depending on rear axle ratio, the transit buses could muster about 55 mph or so; the lower (numerical geared) Suburban versions maybe 65 on a good day.

I drove for Iowa City Transit in 1975-1976. There were 12 of the smaller 35′ long and 96″ wide buses like this one, and two of the TDH-5304 big boys: 40′ long and 102″ wide, and with the bigger 8V-71 engine. The 35 footers were pretty nimble compared to the forties, and one could whip them about pretty quickly in some of the older narrower streets of town. But the slightly newer 40 footers had one other nice feature in addition to the bigger engine: the throttle pedal was air actuated, instead of the mechanical linkage of the older buses. Not only did the mechanical linkage engender knee-ache (to go along with the back ache from the mechanical steering), but one jammed up on me one memorable day. E-pedals were still an engineer’s dream.

The bus in the upper photos has been converted by an enthusiastic Oregon Ducks football fan for game day parties in the parking lot. It also has a smaller non-stock steering wheel, which makes me suspect it has power steering. The other bus, an old left-over from Eugene’s fleet of these 4523s is the victim of a botched conversion attempt, not an uncommon thing. How compelling it is to buy an a tired old transit bus with millions of miles under its belt to convert to the ultimate get-away vehicle. Some have the resources; others don’t, as these two variations of the theme illustrate graphically.

I’ve been tempted to go down this road myself, especially with a handsome PD 4104 conversion. But it’s probably a good thing I’ve resisted, since I like to take my little Chinook in places a 35′ bus would never get out again. But whenever I see one, it does tug on my heart.

I got distracted on RV conversions, and forgot to talk about how GM’s bus hegemony fell apart. It fell victim to the same factors (and others) that undid its car (and big truck) market share: sinking reliability caused in part due to government influence. Since the feds fund the overwhelming share of all transit capital expense (but not operating costs), they started meddling early on with the bus designs themselves. The biggest one was the Transbus project to develop a new generation of buses in the seventies. GM’s proposal for that ill-fated boondoggle evolved into the GM RTS bus.

I’m not exactly an expert on this, but it arrived with complications and issues, unlike the New Look buses. The Canadians (wisely) wanted no part in this new generation of buses, and kept the New Look in production for decades. The RTS had a very checkered career, and eventually GM got out of the transit business, selling the RTS design to MCI, which eventually passed it along again. It was an unloved child that ended up in four foster homes before it was finally surpassed by newer and more desirable designs.

Greyhound never got over its problems with the GM Scenicruiser, and got into bed with with MCI, which has built almost all Greyhound buses until recently. And Trailways had a long love affair with the legendary German designed Kassbohrer that became the American Eagle. GM’s near-monopoly scared the two big bus companies into alternatives, and GM’s coaches eventually fell victim to a shrinking market and lack of development and conviction on GM’s part. Sound familiar?

More new Curbside Classics here