An aquaintance has purchased a nearly new Vectra ('51 reg) with an auto gearbox. He has owned autos for years, and every one did not run backwards downhill when in Drive. Except this one. He has exhausted the local Vauxhall dealer, they have referred him direct to Vauxhall, who say that the new gearbox does not have antirunback feature as a fuel economy measure.
Can anybody with similar car advise ?
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I don't think 'antirunback' has ever been a 'feature', more a by-product of the torque converter. There are many autos coming out now which do away with the torque converter and use clutches, also there is a CVT Vectra which also has no TC.
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I don't think 'antirunback' has ever been a 'feature', more a by-product of the torque converter.
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"Antirunback" is usually a feature of one-way clutch in the geartrain. The TC reactor is usually mounted on a Sprag clutch (one-way clutch) - but this is to enhance torque multiplication at high turbine-to-impeller speed differential and has nothing to do with 'antirunback'.
I cannot see how removing this antirunbaqck feature would help fuel economy. On a hill you would have to keep the engine reving to stop the car rolling back, rather than just letting it hang on the one-way clutch. This would waste fuel and overheat the ATF.
I drove a 2003 model Vectra in the summer and it did indeed have antirunback feature - don't know about 2001 model though.
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I drove a 2003 model Vectra in the summer and it did indeed have antirunback feature - don't know about 2001 model though.
My 2.2 Vectra Auto (Nov 2000) will generally creep forward on shallow hills, but if a quiet steep hill it will roll back if left in "D" on tickover. My parents 1.6 Astra Auto (2001) will roll back on the slightest of hills though.
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My 97 Mercedes 5 speed auto also rolls very slowly backwards given a steep enough hill. I've always seen it as a natural result of the torque converter's limited power transmission at idle, and nothing to worry about.
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The 2000W 1.8LS Estate Auto that my brother drove until recently also used to roll backwards at tickover in drive, on even quite gentle inclines. All it took was gentle pressure on the throttle to bring the revs up slightly to 900 or so, and the car would then hold.
His previous 1998T 1.8 LS Estate Auto, 1995 Sharan 2.0 Auto, and various Astra Autos before that, all behaved the same way. It was only on very gentle inclines that enough torque existed to hold the car, and none of them appeared to have an anti-rollback feature.
Have not tried this in the 2003 V70 D5 Auto he drives now.
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Strange
2003 Vectra auto I had was a German market model. I took it through the Bavarian Alps, over Fernpass etc. - some very steep hills and I can assure you that it did not roll back (even with 5 adults and luggage!).
Older transmissions like the ZF4HP14/18 and 4-speed Jatco's have what they call an 'overrun clutch' (actually a one-way clutch) on the forward gear output stage, this stops the car rolling back. In fact if you drive up a hill and take your foot off the throttle the car will roll back slightly and then come to a stop as it 'bounces' on the overrun clutch.
The latest GM 'boxes have what I believe they call 'hill hold' - this is essentially an electronically controlled clutch which is engaged to lock the geartrain to the transmission casing. Whether this is installed for some markets and not others I don't know.
In the case of CVT with powder clutches (i.e. Fuji unit used by Subaru and Nissan) a small current is fed to the clutch to ensure 'hill hold' at idle.
As to older GM 'boxes, I'm sure the GM125 (old Astra) 'box had one-way cluth in geartrain. Can't speak for later AF13 (Aisan Warner) etc.
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Yes, recent GM / Vauxhall autos do have an economy device fitted. All Astra Mk4 with auto have this, I'm not sure when the Vectra aquired it.
When stationary in "Drive", with foot on brake pedal the gearbox engages neutral instead of using the engine to fight the brakes. When the brake pedal is released, first gear is engaged and off you go. If you don't use the brake pedal the box doesn't disengage.
There is a fraction of a second when the car may move back on a hill after the brake pedal is released but this can be overcome using the handbrake.
I'm not aware of a "hill-holder" device fitted to any Vauxhall, ie UK spec GM vehicle.
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Yes, recent GM / Vauxhall autos do have an economy device fitted. All Astra Mk4 with auto have this, I'm not sure when the Vectra aquired it.
My Vectra (reg Nov 2000) has it.
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>> Yes, recent GM / Vauxhall autos do have an economy >> device fitted. All Astra Mk4 with auto have this, I\'m not >> sure when the Vectra aquired it. My Vectra (reg Nov 2000) has it.
The trend seems to be going that way, my mates E class auto holds on hills fine.
Whats the point in having an automatic gearbox if you have to use the handbrake everytime you stop on a hill ?
Everyone seems to be building semi automatic boxes, that reviews say are no good!
Who makes the best auto boxes anyway?
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The point is that the modern autos give an extra choice. You don't have to use the handbrake on a hill if you don't use the footbrake either and just let the engine and torque converter do the job, just like it always did. You can choose to use foot brake on the flat and not use it on a hill.
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