Do you let it roll downhill in neutral to gain extra speed? I do, shame on me.
I remember my cat C instructor telling me I should never coast even when approaching a traffic light or knowing I’ll be coming to a stop but he couldn’t exactly explain why, he just said something ‘not allowed to do’. He was a dork, though so I pretty much ignored everything he told me. Another one was always select your gear before going uphill, like I know exactly how steep the hill is, and never change it halfway through also whatever gear you go up stay in the same gear for the descent. Obviously coasting downhill in a fully loaded truck that I wouldn’t do but if 50% or less loaded then I let it flyyyyy
ETS:
Do you let it roll downhill in neutral to gain extra speed?
Don’t you mean “take money out of your pocket”?
I remember my cat C instructor telling me I should never coast even when approaching a traffic light or knowing I’ll be coming to a stop but he couldn’t exactly explain why, he just said something ‘not allowed to do’.
Ignoring any legalities…
You use more fuel in neutral than in gear. You don’t have any braking from the engine so you use more foot brake which means they wear out faster and you are more likely to suffer brake fade on a long descent. One thing to do it in a car, a different thing to do it in something which even when empty can weigh 5/6 tonnes up to as much as 21 tonnes. Escape run off areas at the bottom of hills are built for idiots like you.
If you can’t work out why you shouldn’t be doing it in a lorry you shouldn’t be in one.
Conor:
You use more fuel in neutral than in gear. You don’t have any braking from the engine so you use more foot brake which means they wear out faster and you are more likely to suffer brake fade on a long descent. One thing to do it in a car, a different thing to do it in something which even when empty can weigh 5/6 tonnes up to as much as 21 tonnes. Escape run off areas at the bottom of hills are built for idiots like you.
If you can’t work out why you shouldn’t be doing it in a lorry you shouldn’t be in one.
Thanks, I already know that and the question was never about long descents but for short ones hence me PURPOSELY doing it to ‘gain speed’ which I probably wouldn’t want on a 10% descent for 5 miles where I’d put it in low gear and engage the exhaust/engine break and keep my speed under control by applying the foot brake as necessary.
Now explain to me again, why shouldn’t I switch to neutral 50-100m before a red traffic light and come to a stop with the brakes, after I’ve slowed down in high gear before that? According to my instructor I should instead down shift and then clutch+brake to a stop only for the last few meters. Both methods cause wear and tear - one on the breaks, the other on the clutch/gearbox. Enlighten me with your celestial understanding of mechanics. Oh, yeah, fuel saving…lol. Says the guy who admittedly drives slowly on purpose to earn a few extra pennies for himself at the exepense of his employer but at the same time is very concerned about saving a few spoonfulls of diesel over the course of his (artificially extended) shift.
It’s not about money, it’s about control and to a lesser extent wear and tear.
The engine gives you an additional means of braking, both from engine resistance and an exhaust brake (some might say they are the same thing. Whatever). Kick the stick out on a long descent and you only have the foot brake. If they fade out on you, you’re buggered. Forget the park brake, as they are the same friction material. And you’ll not get it into gear without revving the engine, but if you’re doing over the governed speed the limiter will not allow you to rev the engine.
As for coasting any distance up to some lights, be prepared to stop at any time, but also be prepared to keep going at any time too. You’ll do this better if you’re in an appropriate gear right up to the last couple of seconds when you absolutely have to stop.
Sadly, it seems the ability to drive stick is a dying art, with the rise of self shifting manuals.
When I took my class 2 test it had been hot all week and rained hard on the day of test. When I did the emergency brake test I dipped the clutch to early and the drive axle locked up causing the truck to slide, I thought I’m not even going to get out the test centre, the examiner told me why it had happened told me to calm down for a minute and let me carry on with the rest of my test. When I’d finished it the examiner said the only reason I was allowed to carry on was because I controlled the slide hence when ever I drive a manual gearbox I never coast, if you ever have a wagon slide on you unexpectedly you’ll understand why.
“Georgia Overdrive” is an expression relating to a habit by some old truckers of kicking their semi truck into neutral and letting it roll downhill (supposedly to save fuel, but I think they just wanted to see how fast they could roll w/out risking over revving the motor).
Back when I were a lad plenty of us used to have a bit of scotch booster, but the roads were a lot quieter then and you could pick your place so you could see far enough in front to slow down without knackering the brakes. I wouldn’t do it now though. It’s also true that in modern motors you use less fuel by keeping it in gear with your boot off the pedal.
Times have changed, years ago silent 9th was the term for knocking it out of gear and was mainly used to get max speed to get up the other side in your underpowered piece of carp.
Then people started to say it saved fuel, but the engine is idling and idling uses fuel, on the over run ie in gear down hill no throttle it wont be using any fuel at all.
Then they cam out with semi autos that actually drop the truck into neutral going downhill to save fuel!
Lots of trucks are pretty clever and will suss you are getting free momentum and engage the compressor and run the air pressure right up to and beyond its max, as it is getting the air for free ie no fuel used so you save on fuel when you need air.
Yawn, more tripe and ■■■■■■■■, but we’ll try and make some sense from it out of respect for newer lorry drivers who might think doing this is a good idea, it isn’t.
Aberdeen Overdrive was one of the terms used, and if you drove something with a Gardner engine chances are it was flat out at 50mph if you were lucky, and died if it saw a hill, so if on a quiet stretch of road (which before the country was flooded with imports was the norm) you had the chance to build up some speed you’d take it, could make the difference of not dropping to 12/15mph or less on a long incline, so if you could use higher speed to get half way up that hill opposite you’d take it.
Several reasons you don’t do it any more if you have any sense which it appears is lacking here, traffic density, driver density (the ones behind the wheel of the lorry), vehicle recording technology , traffic recording devices eg cameras possible lack of gearbox lubrication without the input shaft turning, but most importantly lorries now have adequate torque and sensible gearing so you’d be probably doing well in excess of 100mph to be overrevving anyway so no point.
As for dropping it out of gear and coasting then using the brakes alone to slow or stop, well that’s how cars are driven by using the brakes alone, it isn’t clever it’s unskilled and typically poor driving standards when applied to lorries, which are usually fitted with expensive efficient auxilliary braking devices to help slow the vehicle, which if used properly (by a lorry not car driver) using the correct gear to maximise retardation will allow smooth economical slowing down with minimal or even zero use of the brakes.
Another problem of coasting in neutral is that if you are using your brakes a lot, you will run out of air. This might have been more of a problem in older trucks; I don’t know.
Ever throwing it out of cog. I’d downshift up to lights, junctions, roundabouts as I saw fit and then kept rolling at a walking pace until it was clear for me to get going again. I rarely stop the lorry at all, I’ll always be moving forwards 90% of the time.
Include reversing too, clutch right out on tickover left foot on the floor and backwards she goes. Best way I know to back down a steep ramp onto a loading bay.
I can only assume this is some sort of bait to see how many old school drivers will bite?
I drive a 16 spd manual, I’ve learnt to never coast, you can feel the weight pushing you on and if you don’t bring the revs down enough it wouldn’t actually go into gear. I can get it to over speed in top gear downhill if I leave the exhaust break off if I wanted too anyway. Stopping for lights/roundabouts I always go down the gears, the engine brake is nearly sufficient enough to bring the truck to a stop it just takes some forward planning, it does wind up the auto box jockeys behind but we all end up stopping at the same light, I try to time the light change so I don’t physically have to come to a dead stop, makes pulling away a lot easier.
Juddian:
Yawn, more tripe and ■■■■■■■■, but we’ll try and make some sense from it out of respect for newer lorry drivers who might think doing this is a good idea, it isn’t.
Aberdeen Overdrive was one of the terms used, and if you drove something with a Gardner engine chances are it was flat out at 50mph if you were lucky, and died if it saw a hill, so if on a quiet stretch of road (which before the country was flooded with imports was the norm) you had the chance to build up some speed you’d take it, could make the difference of not dropping to 12/15mph or less on a long incline, so if you could use higher speed to get half way up that hill opposite you’d take it.
Several reasons you don’t do it any more if you have any sense which it appears is lacking here, traffic density, driver density (the ones behind the wheel of the lorry), vehicle recording technology , traffic recording devices eg cameras possible lack of gearbox lubrication without the input shaft turning, but most importantly lorries now have adequate torque and sensible gearing so you’d be probably doing well in excess of 100mph to be overrevving anyway so no point.
As for dropping it out of gear and coasting then using the brakes alone to slow or stop, well that’s how cars are driven by using the brakes alone, it isn’t clever it’s unskilled and typically poor driving standards when applied to lorries, which are usually fitted with expensive efficient auxilliary braking devices to help slow the vehicle, which if used properly (by a lorry not car driver) using the correct gear to maximise retardation will allow smooth economical slowing down with minimal or even zero use of the brakes.
Excellent post Juddian. Knocking it out of cog wasn’t everyday driving, if your on the M1 and yer old Atky which would do 45 mph at 2100 was going down hill and getting close to 50 mph and the Gardner engine is screaming so in order to stop the con rods coming through the crankcase you can apply the brakes or select that silent 9th. ( though IIRC my David Brown only had 5 gears so it would have been silent 6 th )
The point i’m desperately trying to make is coasting was only done in controlled (somewhat) circumstances . Today’s engines are doing top speed at way under their maximum revs so not much danger of engine damage.
It wasn’t illegal to coast in the UK but ii"s illegal to do it here in the US. (Another useless fact )
Its to do with your compressor. If you are coasting (ie on tickover), you aren’t building up air as quickly. At a time you are possibly using more braking…
Another by product of non use of the “Aberdeen Overdrive” is that you no longer see trucks stationary at the roadside with the prop shaft trailing on the deck and a trail of sundry bits of metal.
There were several other reasons against knocking it out of stick as have been mentioned but it was often frowned upon by operators as considerable damage could occour when attempting to get it back into cog and totally cocking it up! Some companies even put a sign in the cab; “Do not coast in neutral” which sometimes got the reply from the driver “Sorry boss, but I don’t know what other gear to coast in?”
, traffic recording devices eg cameras 
possible lack of gearbox lubrication without the input shaft turning, but most importantly lorries now have adequate torque and sensible gearing so you’d be probably doing well in excess of 100mph to be overrevving anyway so no point.
Some companies even put a sign in the cab; “Do not coast in neutral” which sometimes got the reply from the driver “Sorry boss, but I don’t know what other gear to coast in?”