My 1964 AEC Mercury was good for just under 70mph but there were flames coming out of the exhaust over 65.
I once took a Mk1 Atki 8-wheeler on a changeover from the Forest of Dean to Oxford on nights and got the needle all the way around the dial before I lost my bottle & backed off.
ERF B series with a Jennings sleeper. and a coach Diff that thing would fly until you met a slight hill 
and rumour has it that I may have exceeded the speed limits by accident on many occasions on the flat 
the maoster:
sandgrounder:
weeto:
Saaamon:
Conor:
Saaamon:
I wasnt being funny btw just interested, never knew it was bad for mpg and engine i must say.You’re quite clueless really aren’t you? And I bet you think you’re a professional driver as well…
God no, im far from professional, only been at it a couple of years, what do you expect?
Your gonna have to educate us Conor, as for the life of me I can’t think why running down windy hill at 62 mph is gonna use more fuel and damage the engine!
Yes please educate us in this theory!
I think his point was that if you knock it into neutral (silent seventh
) the engine actually uses fuel to tickover, whereas on the overrun in gear no fuel is used.
That’s my take on it, but we are talking about Conor here so whatever he says will usually be slightly wide of factual but stated with the utmost certainty and belief in the correctness of what he’s written.
Maybe like you say he was going on about knocking it into neutral, but i think it goes without saying thats very dangerous. I normally hold it at around 60 but sometimes go abit faster if i want to get past someone but only have a 1 or 2 click advantage etc.
the maoster:
sandgrounder:
weeto:
Saaamon:
Conor:
Saaamon:
I wasnt being funny btw just interested, never knew it was bad for mpg and engine i must say.You’re quite clueless really aren’t you? And I bet you think you’re a professional driver as well…
God no, im far from professional, only been at it a couple of years, what do you expect?
Your gonna have to educate us Conor, as for the life of me I can’t think why running down windy hill at 62 mph is gonna use more fuel and damage the engine!
Yes please educate us in this theory!
I think his point was that if you knock it into neutral (silent seventh
That’s my take on it, but we are talking about Conor here so whatever he says will usually be slightly wide of factual but stated with the utmost certainty and belief in the correctness of what he’s written.
Paddy’s overdrive hadn’t even been mentioned by that point, perhaps it’s just Conor’s way of boosting his ego by trying to belittle some one less knowledgeable!
Conor:
Saaamon:
I wasnt being funny btw just interested, never knew it was bad for mpg and engine i must say.You’re quite clueless really aren’t you? And I bet you think you’re a professional driver as well…
And you are, are you conor. He asked a reasonable question your a very nasty person, but I am sat here at Gordano with nothing to do so I await to be educated as to why going over 60 downhill is bad for mpg and for the engine. Carry on.
I used to work for a guy who had a few tippers…one of which was an early ‘E’ reg - just before limiters had to be fitted. This thing was a Seddon 301 with a ■■■■■■■ 250 and Spicer box and was affectionately known as The Shed… She was 10 years old and had had the guts flogged out of it since the day it was new and generally mistreated and abused like you wouldn’t believe! She looked a complete wreck but drove like a dream
Down the slip road onto the M4 and give her some beans…once she was up to about 65 just pop her into top and let her have her head… 
I remember having a Leyland buffallo in the early 70s that would fly , sheepskin rug over the engine cover in middle of the cab and my dog sat upright in the middle on the sheepskin whilst we battled on up hill and down dale on the motorways at 80 mph. That was the life King of the road , and yes also young and fearless. now i get the bends at owt over 38mph
i remember picking a sacked drivers daf 85 up from london he was a tramper and i had jst been given it up to newcastle 70 mph lol had to book it off the lad who had it before had been running about for 2 yrs with no limiter hence his dismisal
Bedford TM 4 & 6 wheelers in the forces used to do it.
Got a Scania off the clock one dark morning coming over the A66
WhiteWhiteWhite:
Because we don’t want them to go faster than they should… ““Letting them go down the hills”” is not good for mpg / engine / drivers job !!
Hmm, not quite correct Sir. Downhill is ‘over-running’,and in that state the fuel is circulating
straight back to the tank,not going into the engine. Zero fuel being used.
[check on-board mpg meter for clarification]
and…surprisingly,it’s actually good for an engines’ componants to experience slightly higher revs occasionally.It helps blow out carbon build-up around rings and valves.
Drivers jobs? I guess any weak excuse to fire a guy will do.
206doorman:
WhiteWhiteWhite:
Because we don’t want them to go faster than they should… ““Letting them go down the hills”” is not good for mpg / engine / drivers job !!Hmm, not quite correct Sir. Downhill is ‘over-running’,and in that state the fuel is circulating
straight back to the tank,not going into the engine. Zero fuel being used.
[check on-board mpg meter for clarification]and…surprisingly,it’s actually good for an engines’ componants to experience slightly higher revs occasionally.It helps blow out carbon build-up around rings and valves.
Drivers jobs? I guess any weak excuse to fire a guy will do.
What a load of ■■■■■■■■…
WhiteWhiteWhite:
206doorman:
WhiteWhiteWhite:
Because we don’t want them to go faster than they should… ““Letting them go down the hills”” is not good for mpg / engine / drivers job !!Hmm, not quite correct Sir. Downhill is ‘over-running’,and in that state the fuel is circulating
straight back to the tank,not going into the engine. Zero fuel being used.
[check on-board mpg meter for clarification]and…surprisingly,it’s actually good for an engines’ componants to experience slightly higher revs occasionally.It helps blow out carbon build-up around rings and valves.
Drivers jobs? I guess any weak excuse to fire a guy will do.
What a load of ■■■■■■■■…
As for my last paragraph, for that you may be right!
As for the rest,some research is always a good thing. Just saying.
Hiya …i think you’ll find out that a diesel engine was designed to pull as hard as it could.
yes they are govened… all this limiter is crap for the engine. how many dozers do you see
running on half power…NONE
the leyland 680 engine was never as good in a lorry as it was in a plant vehicle…(bull dozer)
reason been it run on constant high power not slowing down and speeding up, give it some boot.
someone mentioned overun was bad for the engine, where did that come from. its bad to tow
a lorry without taking the prop off. thats why they usuall tow them in with the backend lifted
so running on the fron wheels.years ago fuel was cheap(7p a gallon) so no one bothered about fuel
like today.in 1966 a 180 ■■■■■■■ runnig at 30 ton would only do 3 mpg.
foden two strokes needed to run at high revs(no less than 2300) theirs no way you could limit
a fd engine it needed fuel and revs…70 mph to get any where.High diff.
when peter grimer raced a 362MAN at the truck races, MAN give him a road going unit to get used to
and run in. it did 60 MPH.peter said it need to go faster for the race(obviousley) the MAN fitters opened
up the pump…146 mph just like that. so where dose this overun wreck a engine.
Excellent post
Rikki-UK:
ERF B series with a Jennings sleeper. and a coach Diff that thing would fly until you met a slight hill
Ah the coach diff! When I worked for a long since defunct Teesside haulier I had one of the first 95 Dafs on the road (E985 NMK how sad I still know that?) and that had a coach diff in it and I remember that on a clear run the tacho trace would dissapear off the top of the chart and only reappear upon re-entry! Must’ve easily been doing 60mph
3300John:
Hiya …i think you’ll find out that a diesel engine was designed to pull as hard as it could.
yes they are govened… all this limiter is crap for the engine. how many dozers do you see
running on half power…NONE
the leyland 680 engine was never as good in a lorry as it was in a plant vehicle…(bull dozer)
reason been it run on constant high power not slowing down and speeding up, give it some boot.
someone mentioned overun was bad for the engine, where did that come from. its bad to tow
a lorry without taking the prop off. thats why they usuall tow them in with the backend lifted
so running on the fron wheels.years ago fuel was cheap(7p a gallon) so no one bothered about fuel
like today.in 1966 a 180 ■■■■■■■ runnig at 30 ton would only do 3 mpg.
foden two strokes needed to run at high revs(no less than 2300) theirs no way you could limit
a fd engine it needed fuel and revs…70 mph to get any where.High diff.
when peter grimer raced a 362MAN at the truck races, MAN give him a road going unit to get used to
and run in. it did 60 MPH.peter said it need to go faster for the race(obviousley) the MAN fitters opened
up the pump…146 mph just like that. so where dose this overun wreck a engine.
There is a simple reason why they remove the propshaft or raise the rear wheels off the ground. If you dont, the gearbox may seize up. Many boxes have an internal lubrication pump which only runs when the engine is running. It is cheaper & easier to remove the propshaft then to replace a gearbox.
Modern fuels shouldn’t need the ■■■■■■■■ revving off them to stop them carboning up, we can leave that to the men with the 1950’s decoke sets and valve lappers.
My biggest worry about freewheeling down a hill is that if I need some brakes, I prefer having a full tank of air.
We had a Iveco/Fiat 17-tonner on hire in the 80s. Loaded very little in Southampton then headed back to Merseyside. Oh Lord, did that thing go! Saw 83 before common sense prevailed. Hopes of a record run were dashed by a pickup in Chellaston but we did get a record (for us!) of sorts - most M-ways in a day! (10)
Wheel Nut:
Modern fuels shouldn’t need the ■■■■■■■■ revving off them to stop them carboning up, we can leave that to the men with the 1950’s decoke sets and valve lappers.
Hehehe. This reminded me of my old boss at the garage I once worked at. Little old lady brings her Moggy Minor in - “It’s not running right”. “Leave it with me, Mrs” he says. She goes home, he hands me the keys and says, “Take it down the by-pass, son, and thrash the nuts off it”. Old lady dead chuffed with smooth running Mog and lighter by the cost of a decoke!
WhiteWhiteWhite:
Because we don’t want them to go faster than they should… ““Letting them go down the hills”” is not good for mpg / engine / drivers job !!
If your lifting off the throttle your not using any excess fuel, and as for being bad for the engine its only building up revs not creating any engine load. It wouldn’t cause damage.
Letting them go down hill will have zero effect on fuel consumption, except it may use a little less as momentum will get the lorry up the other side or further along the level rather than diesel 
As long as the RPMs are under the maximum rated speed of the engine it will do it no harm at all
However as White’s run over the water, an overzealous copper could have a sense of humour failure and that could mean a big fine and possible delays to the journey
They also have an O Licence and VOSA do not like speeding lorries, so systems must be in place to combat this, a smart phone alert is such a system and will keep VOSA happy, which is no bad thing