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Rover 75's have a transmission tunnel because they used the BMW 5 series floor pan, to save on having different parts presumable and also it will make a for a stiffer floor.
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I remember when front wheel drive first came in in a big way - Mini, 1100 etc - it was blazed as signaling the end of transmission hump and tunnel, with much more space inside the car. Since then manufacturers have gradualy re-occupied the space, so cars are as cramped inside as the old ones used to be.
But neither design actually has to be that intrusive. My Triumph 2000, although having a conventional gearbox and propellor shaft, in fact has a relatively small hump and lots of space between the front seats. It is for example quite easy to walk through from the back to the front, with the handbrake folded down to the floor.
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Richard Woolley the designer of the 75 himself commented a few years ago on this rumour that had been doing the rounds for year - the car does not use the old 5 series floor pan, or any other BMW floor pan. The 75 like many fwd cars has a central tunnel.
hth
R40
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No tunnel might have made the 4.6 V8 versions of the 75 and ZT a little less likely!
The Mondeo I/II floorpan had a tunnel but then there was a 4wd version of the MkI, the Mondeo III floorpan is also used in the X-Type which was 4wd only at launch, the Golf/A3 etc floorpan facilitates 4wd etc, 4-Motion, S£, Quattro etc, likewise A4 etc ...
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Facilitates 4wd variants
That's the most likely cause.
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I would agree that the Mondeo might have had a planned 4x4 variant from the outset. And it did have at least one - the 4 wheel drive X-Type. The platform could have been used for other cars too but could not give examples.
The new Mondeo platform is used by Volvo and so 4x4 variants possible.
I too remember the big deal of the Escort when it went FWD. The "bump" where the transmission tunnel would be was very low. And as others say over the years the tunnel has come back even for FWD... we have to blame platform sharing for that then.
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You would`nt want the exhaust totally exposed hanging below a flat floor pan.
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Strengthening was the received wisdom back n the eighties when it all went crazy and the cars were dragged along rather than pushed. Number_Cruncher will be here in a minute though.
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A car with a transmission tunnel feels like a real car to me, not some king of flimsy skip.
The XJS had a wonderful, wide, solid tunnel. Short gear selector, lots of knobs.
I hate flat-floored cars with a skinny gear stick that's nearly two metres long.
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You would`nt want the exhaust totally exposed hanging below a flat floor pan.
Like a Renault 4 perhaps? And of course proper cars that have a propellor shaft in the tunnel instead.
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"Richard Woolley the designer of the 75 himself commented a few years ago on this rumour that had been doing the rounds for year - the car does not use the old 5 series floor pan, or any other BMW floor pan. The 75 like many fwd cars has a central tunnel."
You correct
History
The Rover 75 started life as a project for the complete re-skin of the Rover 600, under the control of Rover Group designer Richard Woolley,[2] but following the BMW takeover it was quickly decided that the Rover 600 would not be re-skinned but replaced by an entirely new model. Work on the new model, codenamed "R40" progressed well with little or no interference from BMW, with the basic design having received an enthusiastic response from BMW management and both BMW and Rover believing that a retro design would be the ideal choice for Rover. Press speculation mounted towards the launch that the 75 was based on the BMW 5 Series thanks to the central tunnel in the chassis (normally only found on rear wheel drive cars) and the BMW Z-Link suspension from the rear wheel drive BMW 3-Series. The central tunnel was actually built into the chassis to increase structural rigidity.
The first production Rover 75 model, a V6 ConnoisseurThe car quickly attracted praise for its characteristics, including its ride quality, interior, and traditional looks. Critics of the car labelled its styling too "retro", suggesting it had been designed with an older buyer in mind. However, the 75 won a series of international awards including various "most beautiful car" awards, including one in Italy.[3][4]
Assembly originally took place at Cowley, but in 2000, following the break up of the Rover Group and the split with BMW, production was moved to Longbridge.[5] 2001 saw the introduction of the Rover 75 Tourer, swiftly followed by the MG ZT and MG ZT-T. Between 2000 and 2003, there were few changes to the range, the biggest being the 2.5 litre V6 engine being joined by a low pressure turbocharged 1.8 litre, 4-cylinder engine. The introduction of the "greener" 1.8 litre turbo greatly benefited British company car drivers who are taxed on carbon dioxide emissions. A customisation programme, Monogram, was launched, allowing buyers to order their car in a wider range of exterior paint colours and finishes, different interior trims and with optional extras installed during production.
In early 2004, Rover face-lifted the design of the 75 to a less retro look. Rover also added a new trim to the range called Contemporary which featured a more modern dashboard and exterior. This design was given a mixed reception by the motoring press, and Rover announced a new V8 model with a completely different front grille only a few months later. This grille was said to be inspired by the Rover V8s of the past but caused some controversy, being similar to the then new style of larger Audis. A long wheelbase "limousine" version called Rover 75 Vanden Plas ? about a foot longer than the regular 75 ? also adopted this new grille. The Rover V8 grille was made available as an option for the rest of the range shortly afterwards.
Since its launch, the 75 has been one of the most popular ministerial cars in the British Government. Various Ministers are driven around in 75s and Tony Blair had access to a 75 Limousine while he was in power, but was never seen in it.[6]. Recently though, Alistair Darling has been seen in a "V8 Grille" Rover 75 which could be the 75 Limousine. MPs said to have or have had a 75 include:
Patricia Hewitt
Gordon Brown
John Reid
Charles Kennedy
Ruth Kelly
Tessa Jowell
Richard Burden
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Most cars that I have seen from underneath have exhaust boxes that would never fit into the cavity provided by the tunnel.
I have no issue with a tunnel between the front seats, but in the rear, it really does not help. My old 1986 Polo had a tunnel in the back, but that never had a 4x4 variant.
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OTTOMH I think one of the old Toyota MR2s (Mid engined of all things) used the "tranny tunnel" to host the fuel tank.
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Aside from packaging issues with prop-shafts going to rear axles, the primary purpose of the transmission tunnel is to stiffen the floorpan.
Lonitudinally, a transmission tunnel acts as a crush tube, which can initially be rigid and act as a safety cell, but once deformed absorb significant amounts of crash energy.
In a side impact situation, a transmission tunnel offers somewhere for the impacted seat to move into, away from the crash site.
In bending of the floorpan, the tunnel effectively replaces one large plate like structure with two half sized ones - this raises the first natural frequency of the floorpan significantly. As bending vibrations are the ones which couple most effectively with sound, this is also a good thing for NVH.
Going further, a stiff floorpan also reduces the problem of scuttle shake, and contributes to overall body stiffness. Where the ends of the transmission tunnel are effectivey built in to the remaining structure, there is an enhancement of torsional rigidity - if the ends of the transmission tunnel terminate in unsupported panels, there's no torsional rigidity gain.
Number_Cruncher
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On vehicles with no risk of a rear wheel drive, why not a " transmission" trough ?
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drive why not a " transmission" trough ?
Good idea though it would drag on the ground ;-)
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