A technical and historical review of GM's most controversial platform
May 22, 2011
By Mark Cadle
In 1980 or thereabouts, GM Holden was in pretty much the same orbit as other GM divisions: building localised versions of GM platforms developed elsewhere, with largely homogenous GM styling. It's first such model in 1978 was the Commodore, a cut-and-shut of the budget Opel 4-cyl Rekord and luxury 6-cyl Senator; using the solid axle from the former and front section to turret from the latter, it had a rocky start. GM told Holden to build it - wrong car, wrong time. Too small and a knee-jerk to the oil crisi of the 70's that was over before it arrived.
Holden almost went broke. GM to it's credit recognised where responsibility lay, and brought the company back into solvency; also cutting Holden from the fold. No more just a division, now a subsidiary - it's own company, but owned by GM. This was also a lesson: one mistep could be the end.
Sideline: a young German Engineer who came over with the first prototype Commodores made in Germany (only to see them fall to bits on Holden's test track!) was Peter Hannenberger, later to be Holden CEO during the heydey of the V-car in the 90's and early noughties, with the introduction of Monaro.
In the 1990s, Holden came of age as a standalone carmaker. The model derived from the Opel Omega aka Cadillac Catera, had bulked up like the Incredible Hulk; it transmogrified into Australia’s best-selling car, the VT Commodore in 1997. Bigger, wider than any Opel version; about 50% larger in gross vehicle mass and importantly with the addition of V8s and long-wheelbase and commercial models, it was also sold in many more variants than Opel ever envisaged; before signing out in 2006.
New V8s arrived from America in 1997 – the all-alloy LS1 with (initially) 305hp. Coupled with a LWB-chassied Statesman/Caprice formed by adding a fillet to the floorpan of the GM2800 to produce a long limousine variant, along with the wagon and Ute; soon to arrive in AWD capability, things were looking up and up for Holden. The factory at Elizabeth was to turn out 280,000 of these between 1996 and 2000 - basically working every available hour. These were the salad days: they struggled to make enough cars in enough versions.
The Holden VT Coupe Concept which wowed the 1998 Sydney Motor Show, and events like Australian ‘Motor’ and 'Car UK‘ magazine's shipping of a HSV VT GTS with the Callaway C3 400hp LS1 to the Nurburgring in 2000, where back-back it crucified the BMW M5 and AMG E55 in every performance measurable, contributed to an increased appreciation of GM’s standalone Down-Under division.
But they had a problem: the Opel Omega, the original GM2800, was dying at the same time the VT was introduced; no more German RWD, IRS tech. The semi-trailing arm rear was on the way out anyway with most makers for inconsistent geometry on travel and high unsprung weight; and Macperson front suspension was old-hat.
Plus modern multilink IRS designs, as well as better ride/handing, take up less space under the car; important for packaging (Commodore's fuel cell is under the car where the VT-VZ rear suspension mounts were), and offer near-constant geometry. With Opel eschewing RWD for a FWD future, and GM North America lacking any mainstream applications (having killed the last B-body in 1996, and fortuitously handed the Middle East market to Holden) Holden would have to ‘roll-their own’.
Holden had remade the Opel chassis: the fours and inline sixes of the Opel had given way to the GM 3800 iron V6, and then the HFV6 all-alloy, DOHC in 3.6 litre displacement, and the Holden 5 litre cast-iron V8 to the LS1 5.7 alloy V8. But this chassis was certified to only 400hp, little more than the 380hp Vauxhall Lotus Carlton, and had limits of payload, external and internal size and towing capability. Holden had added AWD with several models.
They needed something else. It’s projected death was 2005 – in Holden’s hands it had been a far more significant unit than for Opel, for whom it had effectively died almost a decade earlier.
GM initially commissioned Holden to produce Sigma with the aim of sharing with Cadillac, a chassis with alloy double A-arm front suspension.
For whatever reason, the partnership was dissolved: Sigma as specified by Cadillac for the CTS and STS could not form the basis of Commodore – too narrow a track meaning limited width and rear-seat space, and the insistence of Cadillac on a high firewall to suit the SRX SUV, meant GM subsumed the development. Plus the forged alloy double-wishbone suspension system was unsupportable at entry/family Commodore pricing points. To underline Holden's quasi-independence from GM, it simply decided to go it alone; using lessons learnt from working on GMT2800 and Sigma.
In GM’s scientific Greek-alphabet naming scheme, Zeta was appellated – to Holden insiders, it was just ‘Commodore’. This is the first time that Holden has really designed a new vehicle chassis completely from scratch: the original Holden, the 1948 48-215 or FX, was a re-jigged pre-war unibody Chevrolet engineered in America up to prototype stage. Every Holden since then was been derived from another GM design in some way: right up to the Commodores of the 1980’s and 1990's.
Holden’s Billion Dollar Baby - first of a series of infomercials Holden made to introduce the VE Commodore to the Australian public.
Zeta uses lessons learnt from Sigma and other developments (Holden and GM affiliates worldwide share resources: Holden employees work on many GM international programs). Australians are very pragmatic. ’Keep it simple, stupid!’ might be a national motto.
So Zeta uses a simplified 4.5 link Independent Rear Suspension (IRS) and a Short Long Arm (SLA) dual-pivot front suspension, which marries the simplicity of Macpherson struts with the superior low-scrub, constant-geometry (planted contact patch for tyres) of a double-A-arm setup with a 'virtual pivot' at the top of the stub axle.
Double wishbone, alloy A-arm forged and cast/fabricated suspension as fitted to CTS Sigma. Very nice, but not cheap.
The stub axle on the left is SLA: the top stub-axle pivot replicates a double-wishbone setup, at lower cost; with simpler mounting system. Stub on the right is a conventional Macpherson, a good basic design but not state-of-the-art in performance.
Advantages over Macphersons are less scrub (steering pin angle close to tyre contact patch) and the geometry can be arranged so the wheel stays perpendicular to the road, even with body roll or suspension travel. This means fewer tugs at the steering wheel on bumps and less tramlining, lower steering effort especially when going fast and improved feel and control at wheel. You aren't twisting the Macpherson strut's oil seal/bushings to turn the axle.
Ultimately, it contributes to ride, steering coherence and on-the-limit grip. many people note the Commodore's light steering, confusing it with over-assistance or lack of feel. In reality, it is low steering effort. There is a reluctance to self-centre from extreme lock, a known SLA behaviour but hardly a problem.
The car packaged necessary improvements in space, safety and power; modelled in cyber-space on GM’s new FEMs virtual reality workstations. These meant simultaneous teams can work on the car in real time, developing substructures, fittings and components as well as the ways to build the vehicle on a production line as efficiently as possible.
Low-carbon (Blue) High Strength (red), Advanced High Strength (orange) and Ultra-High-Strength (Yellow) Steel. 600hp is within it's capability due to it's rigidity, as well as maximum crash safety ratings.
It is produced on a "modular" system of body assembly. This means you have side modules (one piece panels) a front module consisting of the suspension horns, rear module with rear horns and the trunk floor/spare wheel opening, and a roof pressing.
These are clamped together like your first High School woodcraft pencil box project. Six elements including the floor an roof, then autobot welded. The result, coupled with Holden innovations like variable-length front horns and floorpan mean Holden can produce a variable wheelbase product – vary the length of the horns for longer front axle-to-dash/shorter greenhouse proportions for Camaros and coupes. Shorter nose for Commodore, or for a SUV or cab-style pickup. Indeed, it's unfortunate that Zeta's true potential will likely remain unrecognised - not due to any failing on it's part, but GM's bankruptcy; and paucity of funds to realise the different versions it could have been created in.
Such is the strength of the body understructure, that the front guards contribute almost nothing to the crash ratings: they could be replaced by plastic or alloy tomorrow; Holden's engineers are confident the car will still cakewalk frontal collision tests.
Without re-engineering the structure Holden engineers have told me by varying the lengths of the floor sections and the 'horns' they can produce a wheelbase going from less than 110" or around compact sedan/coupe up to over 120", for a stretched limo or large SUV or unibody truck. And be confident it's power-handling capabilty, load-carrying/towing ability and crash rating is not affected. Track can vary within a range of several inches with different axle assemblies.
It also meant at one stage Holden were in the running with a modified Zeta for an Alpha contender – the 2004 Torana concept was an ambit built off Zeta, using Solstice front suspension bits. As late as 2009 Lutz was quoted as saying ‘we might build Alpha off that Holden concept’.
The Bigger Picture: Best Laid Plans
To understand what Holden intended with Zeta, you have to understand Holden’s product portfolio, and where it was at during Zeta gestation. Unlike many conventional car plants, which might produce a sedan and perhaps a coupe and/or wagon, Elizabeth has to produce an amazing array of cars to meet Holden's marketing needs at home and abroad.
With the older, 1996-2006 V-car chassis that underpinned the VT/VX/VY/VZ Commodore, up to 65 variants of vehicle in three wheelbases, six body styles 2WD and AWD, LHD and RHD were produced at one time: and sold as nine or more brands if you count HSV on five continents. There were also no less than three suspension variants, with IRS, leaf-spring and alloy suspension models.
Walk into Holden Vehicle Operations:Elizabeth in 2005, and you might see any, or all of these configuations being made. And not only as right-hand-drive Holdens! Sedan, Ute, One-Tonner (tray), wagon, coupe, AWD HSV Coupe, 2WD Crewman, AWD SUV, AWD Crewman. Zeta was planned to be produced in a similar array - just not all at Holden.
Holden is a small auto company, and has one engine plant and one vehicle plant. So it has to maximise flexibility. From day one VE was intended to produce sedans, 2wd and AWD wagons, at least one utility-type in 2WD and AWD, a coupe, several longer-wheelbase versions and other derivatives. Some of these were by design export variants for the Middle East, US, South America, Asia and even potentially Europe – the Middle East alone largely paid for the WM Caprice with projected sales volumes.
Many of these models have unfortunately not transpired. But that isn't due to lack of effort on Holden's part.
Coupe60 was a 2008 Melbourne International Moto Show concept, built off the abandonned Zeta GTO/Monaro prototype. Fullsize mockup, but an unfinished shell. Ford was gnashing teeth again (introducing updated 2008 FG Falcon). Another scene-stealer, this time unfortunately stillborn. Holden did it as a present to fans: 60th Anniversary of Holden, 40th Anniversary of original Monaro, 10th Anniversary of VT Coupe Concept.
The US Connection
Zeta is a controversial topic in North America. From the days before the GTO landed to a mixed reception, GM planned to use it for virtually every brand – including a GMC Denali unibody ‘truck’, possibly.
The following are just some Zeta models informally confirmed - this is not an exhaustive list:
GMX511/521 Camaro coupe/convertible.
GMX551 Impala sedan.
GMX553 Lucerne fullsize replacement (Caprice-sized).
GMX556 was the DT7, a DTS/STS replacement (Caprice-sized).
Ever wondered what the Zeta Cadillac might have looked like? These GM models from the Advanced Design Studio give you an idea of what GMX556 might have been. They aren't toys or whims. Each of these represented a potential Zeta variant.
Then two things happened: the GTO got off to a lacklustre start – it appears the relatively-sedate-by-US-standards-styling, already belonging to a previous generation of cars (and all but finished in Australia); plus the high price and limited options (basically transmission) with no discounts, when US car buyers had been conditioned to be bribed into buying cars was too much for the market, initially.
Strange marketing choices like a majority of auto-trans models didn't help. The smash hit 2005 Mustang was also an unexpected bugbear – being retro-American cool exactly like the Monaro wasn’t.
This cooled GM’s enthusiasm for both RWD, and it’s newly-rediscovered Australian subsidiary which had been beavering – or is it platypussing – away on it’s own for decades. However, unlike the Monaro, the upcoming VE Commodore/Zeta 1 was developed from Day 1 to be not only ambidextrous in driver position, but also designed with US standards and tastes in mind. VT Coupe which came to be the reborn Monaro was never even planned to be made: it went from 1 show concept, to 10,000 Australian units, to around 65,000 examples and export to five continents. VE was ambitiously slated to go international off the drawing board.
If Holden hadn’t lost a lot of allocated funds, which allowed GM finish the important GMT900s in 2005/2005 when VE was in final stages of development, it might have been even more so.
Since the LS1 became available, GM Holden had increasingly become an important customer of GM Powertrain – even if it was a rocky start with the LS1 piston-slap/oiling issues. Apart from that wrinkle, the relationship has been to the benefit of both: Holden is amongst GM’s largest customer of Gen III and Gen IV V8s – and already has the Gen V in mules.
Around 2006, GM started to pay attention to the unavoidable: they were broke, and getting broker. At one stage in 2006, it was estimated they had weeks of reserves and were technically insolvent. Then, to prove it’s either a feast or a famine, the Global Financial Crisis arrived. GM and a host of automakers around the world were in trouble: GM, Daimler-Chrysler, VW/Audi, Porsche (looking to buy VW, but ended up being bought themselves) all needed assistance to survive. GM did indeed go into Goverment-administered bankruptcy. Which unfortunately killed a lot of promising product already well advanced. Like all but one North American Zeta, the Camaro.
So the on-again, off-again US Zeta models meant to share Oshawa with the Camaro were 86’d for good. And that’s a real pity: as anyone privileged enough to see the Zeta Impala, or DT7 Cadillac would know.
And to show how serious GM was at one stage, here is the ‘LWB’ Cadillac Zeta. Yes – there was more than one variant planned.Source: GMI exclusive https://www.gminsidenews.com/forums/f...curtain-97635/[/CENTER]
That forced GM to cancel all but the most PR-sensitive (Volt) and too-far-gone-to-cancel new programs (Camaro). Apart from vehicles due for imminent release like the Malibu, the GMT900s and Lacrosse, everything else was canned – off every platform. That also forced GM to re-evaluate Zeta, and it was a cause for furrowed brows. Zeta was engineered for Holden to be flexible, and to provide many vehicle body styles and capabilities off one basic shell, allowing an uninterrupted array of vehicles and drivelines to pursue each other down the line. Holden or it's closely-allied suppliers make panels, trims, minor components onsite.
Elizabeth plant's Zeta 'Mad Mouse' monorail - computer-controlled and linked to JIT inventory system bodies leave paint shop to assembly plant.
GM looked at Holden's manufacturing methodology and threw it's hands in the air: what works for Holden in it's JIT flexibility would create bedlam at a major US plant. So, much of the automation on Holden's line and VE features like the walk-in front, are missing from the Oshawa Camaro facility. This works for GM, because that line needs produce only two models and is a much more conventional facility.
Zeta assembly: walk-in module and variable-height skillet aid worker tasks.
Robot dash-module insertion through windshield opening: complete padding, instruments, steering column, pedals, aircon, infotainment. No humans on this workstation.
Driveline inertion: a body drops onto the motorised pallet with the complete powertrain from radiator-diff and including front and rear suspension. A worker leans in to move the front suspension in place, then the 'bots fit the dozen or so bolts that mount the whole unit. Saves 8 minutes of labour per car.
Next: Zeta II - The Future
The last word: a German tester compares the Vauxhall VXR8 to the BMW M5 (Zeta 1 rebadged HSV Clubsport).