I’ve thought this DDC lark through a bit more, but I think it might still come down to a “form of words” issue, because there is a lot of sense in a lot of the posts. By that, I mean there seems to be a number of skilled advocates for both sides of this issue.
Perhaps Lucy could do a follow-up interview with “expert No1,” when he has more time, since gardun’s comment about an engineer might well have more merit than I’d at attached to it on my first reading. How’s that for an admission Sorry I missed that gardun
BTW Lucy, that’s got to be up there with the very best in grovelling my way out of missing an obvious way forward
(That one is now copyrighted for my future use, but I might make a small number of licences available to friends who get stuck )
Now I’m wondering where all this might end, or more to the point, who could possibly be the ultimate arbiter that we’d ALL believe??
Gearbox NAH!! More like Pandora’s box Now where’s the referee
I shall endeavour to collar the engineer in question on my return to work (and yes, Dave, that was stunning…hows about you let me borrow it at will and I’ll wave the royalties on all my tactics which you’ve so far stolen. ).
Unfortunately, the man concerned is of the variety whom if you ring him up and say “My truck has broken down” he will say “It shouldn’t have done”…So you say “Well it has” and he replies “Are you sure?” (continue ad infinitum until someone swears and puts the phone down, then ring back and repeat before assistance is finally summoned).
My favourite example of the above was just a few weeks ago, when I turned up in the yard to find no truck. Reply? “It should be there”. Well it isn’t. “Are you sure”…? Well actually no, ***, after all it’s so easy to miss something 13 feet tall, 8 feet wide and painted BRIGHT [zb] YELLOW!!!
Bearing the above in mind, I shall also continue to accost random mechanics/technicians/engineers and pHd-level gearbox designers in an attempt to find someone who will agree with me.
Trying not to get involved here girls but perhaps a more definitive answer may come from somebody at the various manufacturers
Rather the random accosting of people by a stroppy yorkshire lass, a bunch of eee by gum in my day etc and a spattering of MMTM
I would have thought being part of the vast publishing empire that this site is, that access to said channels of info would be possible
I remember back in the late eighties the company I drove for replaced a load of Fuller equipped Bedfords with Mercedes 1625s, These had a straight six gearbox with a splitter. Mercedes provided a demo driver to take every driver out for an hour or two and we were told not to double de clutch or blip the throttle as you were just doing everything twice which wasted your own energy and blipping the throttle made the synchro rings have to work harder too. Also the clutch plates and flywheel had twice as many contact points increasing the chance of the plates slipping causing more wear.
Lucy:
(and yes, Dave, that was stunning…hows about you let me borrow it at will and I’ll wave the royalties on all my tactics which you’ve so far stolen. ).
Hmm… deal or no deal. That’s not difficult Ma’am: It’s a deal.
I think it should become known as the “merit” defence, since it nicely avoids having to admit that a point was missed completely. (Did you also spot the “use of passive voice” tactic??)
Even that defence wasn’t available to me when I suffered a checkmate in the “split shift” question
How about adopting MM’s excellent suggestion of checking with the experts he mentioned? Would that be possible?
At least the protagonists would have their answer…
It’s not a bad idea…But I like accosting random mechanics (not fitters, they just fit stuff after someone else has done the understanding bit…), so will carry on doing that as well.
hey if the industry has such a shortage of new drivers now (even less when the cpc is in place) what would it be like if they had had to learn ddc? It would put alot off. If i’m not mistaken alot are people who think it’s a great paid job or just moving industry isn’t it?
steve07:
hey if the industry has such a shortage of new drivers now (even less when the cpc is in place) what would it be like if they had had to learn ddc? It would put alot off. If i’m not mistaken alot are people who think it’s a great paid job or just moving industry isn’t it?
That’s a fair point steve07, but there’s a lot of us old 'uns on here. When we started, there weren’t many wagons with syncros, so it was either DDC properly, or make lots of embarrassing crunching noises with onlookers laughing their heads off at you. It didn’t take long to learn that way
mikermhh:
I remember back in the late eighties… Mercedes 1625s,… These had a straight six gearbox with a splitter.
Spot-on mikermhh. I remember the 1625. Ferrymaters had some IIRC. I also did Spain and Italy with a 1626 (still gutless even with 10 extra horses.) The one I drove in the early 80’s was a 1977 “S” reg. Your memory of the gearbox is the same as mine, but I didn’t have the benefit of being shown. With that gearbox, you could miss a gear or a split if you were too quick for it, ending up in a false neutral. BTW, this isn’t MMTM
mikermhh:
I remember back in the late eighties the company I drove for replaced a load of Fuller equipped Bedfords with Mercedes 1625s, These had a straight six gearbox with a splitter. Mercedes provided a demo driver to take every driver out for an hour or two and we were told not to double de clutch or blip the throttle as you were just doing everything twice which wasted your own energy and blipping the throttle made the synchro rings have to work harder too. Also the clutch plates and flywheel had twice as many contact points increasing the chance of the plates slipping causing more wear.
Well,I’ve heard some [zb] in my time,but that has got to be the best.And isn’t the last sentence a bit contradictory?,or am I not reading this right?
I drove the same model in the late '70’s on M/E,was conversant with the gearbox,same as in a DAF 2600.Never had any problem,or need a new clutch.
mikermhh:
Also the clutch plates and flywheel had twice as many contact points increasing the chance of the plates slipping causing more wear.
Well,I’ve heard some [zb] in my time,but that has got to be the best.And isn’t the last sentence a bit contradictory?,or am I not reading this right?
That last sentence had me wondering as well…
I’d put it down to it being a difficult subject to put in writing, or maybe an unsure recollection.
Although it doesn’t seem to make sense, it might not be anybody’s fault.
mikermhh:
blipping the throttle made the synchro rings have to work harder too.
This item has realy got me revved up,if you’ll excuse the pun.I can’t believe what I’m reading!Mercedes synchro rings are no different to anyone elses in the way they operate.
Revving up as you change down,IS not as hard on the synchro’s as their purpose in life is to bring the freewheeling gear on the mainshaft to the same speed as the sliding gear,by means of friction.
Revving the engine brings the speed of both gears closer,so REDUCING the amount of friction required to bring them to the same speed,BUT,this does require DDC,as the clutch has to be engaged in neutral when you blip the accelerator to speed up the gear trains close to matching speeds.
Revving up on changdown without DDC WILL make the synchros work harder,but you will not have to slip the clutch as the engine will be going at the speed required for the gear you are now in.
So,in a nutshell,driving with a sychro 'box the way you used to with a “crash” 'box is treating the synchro box with kid gloves,it will never wear out!
Synchro 'boxes were designed to make driving easier so drivers didn’t have to be dead right every gear change,plus you CAN make faster changes,when hill climbing for instance,whereas years ago with a "crash 'box you couldn’t change up going uphill,there was a good chance you would have stopped altogether before you got into that next gear.
Next time your truck with a synchro 'box goes in for a major service,have a look at the gearbox oil as its drained.all that gold dust you see in the oil is what has worn off the synchro rings.
bestbooties:
This item has realy got me revved up,if you’ll excuse the pun.
Brilliant pun, I like it
bestbooties:
I can’t believe what I’m reading!Mercedes synchro rings are no different to anyone elses in the way they operate.
Revving up as you change down,IS not as hard on the synchro’s as their purpose in life is to bring the freewheeling gear on the mainshaft to the same speed as the sliding gear,by means of friction.
Revving the engine brings the speed of both gears closer,so REDUCING the amount of friction required to bring them to the same speed,BUT,this does require DDC,as the clutch has to be engaged in neutral when you blip the accelerator to speed up the gear trains close to matching speeds.
Revving up on changdown without DDC WILL make the synchros work harder,but you will not have to slip the clutch as the engine will be going at the speed required for the gear you are now in.
So,in a nutshell,driving with a sychro 'box the way you used to with a “crash” 'box is treating the synchro box with kid gloves,it will never wear out!
Synchro 'boxes were designed to make driving easier so drivers didn’t have to be dead right every gear change,plus you CAN make faster changes,when hill climbing for instance,whereas years ago with a "crash 'box you couldn’t change up going uphill,there was a good chance you would have stopped altogether before you got into that next gear.
Next time your truck with a synchro 'box goes in for a major service,have a look at the gearbox oil as its drained.all that gold dust you see in the oil is what has worn off the synchro rings.
I’ll go with all of that. It sounds right to me. We await the referee though…
Take it easy , I was only passing on what a Mercedes demonstrater was telling us, he must have got fed up of telling us not to double de clutch as there were 100 drivers and these were the first synchro boxes in the depot!
Taking this subject a bit further a couple of years later, about “88” we got some “1733” with EPS boxes. I loved them but most hated them for being too slow, any thought?
mikermhh:
Take it easy , I was only passing on what a Mercedes demonstrater was telling us, he must have got fed up of telling us not to double de clutch as there were 100 drivers and these were the first synchro boxes in the depot!
Taking this subject a bit further a couple of years later, about “88” we got some “1733” with EPS boxes. I loved them but most hated them for being too slow, any thought?
This might now be a recollection question, because IIRC, you’ll find that “about 88” they would have been a 1735 with the EPS box. IMHO, they had the slowness you noted, but they were an improvement on the older 1633. I don’t remember (not the same as “didn’t exist” ) a “1733” at all, but somebody might put me right… IIRC, the first EPS were made by Merc themselves and were troublesome, but then ZF brought out the replacement EPS and they were much better. It might have been the ZF one first and the Merc version next though…I can’t quite remember.
bestbooties:
…
This item has realy got me revved up,if you’ll excuse the pun.I can’t believe what I’m reading!Mercedes synchro rings are no different to anyone elses in the way they operate.
Revving up as you change down,IS not as hard on the synchro’s as their purpose in life is to bring the freewheeling gear on the mainshaft to the same speed as the sliding gear,by means of friction.
Revving the engine brings the speed of both gears closer,so REDUCING the amount of friction required to bring them to the same speed,BUT,this does require DDC,as the clutch has to be engaged in neutral when you blip the accelerator to speed up the gear trains close to matching speeds.
Revving up on changdown without DDC WILL make the synchros work harder,but you will not have to slip the clutch as the engine will be going at the speed required for the gear you are now in.
So,in a nutshell,driving with a sychro 'box the way you used to with a “crash” 'box is treating the synchro box with kid gloves,it will never wear out!
Synchro 'boxes were designed to make driving easier so drivers didn’t have to be dead right every gear change,plus you CAN make faster changes,when hill climbing for instance,whereas years ago with a "crash 'box you couldn’t change up going uphill,there was a good chance you would have stopped altogether before you got into that next gear.
Next time your truck with a synchro 'box goes in for a major service,have a look at the gearbox oil as its drained.all that gold dust you see in the oil is what has worn off the synchro rings.
Spot on IMHO. We were also advised by Mercedes that on our new trucks we should not blip the throttle as it wastes fuel. This does of course sound good to the boss, and does not take into account who will be supplying and fitting the more rapidly worn out clutch when we all “drag” the engine revs when changing down by slipping the clutch.
To be honest, the wind direction and strength makes more difference to fuel consumptio, as might the weight of the driver
Last Friday I worked a ‘training night’. Now that training is no more than showing a new guy where the drops are, but it got me thinking.
I felt every gear change he made, most down changes felt like the brakes had been slapped on as he was always at least one gear too low. Every time he pulled away, it was with at least 1,000rpm and clutch slip because he was at least 1 gear too high. You could see him forcing the gear lever against the synchro on every down change and the effort used when changing up must have been close to ripping the lever out of the box. Not a single DDC in sight.
Now this is a box I DDC every change and it slips through smoothly with just a flip of the finger tips.
My guess is that the other guy was doing an excrutiating amount of wear and tear to both gearbox and clutch, but on the basis of the arguments against DDC, would that damage be blamed on me for DDC or the other guy?
But what really made me wonder was just how do fitters, mechanics, engineers or anybody else tell the difference between damage caused by abuse or ‘damage’ caused by DDC?
And, if DDC causes damage, why do synchro boxes need less effort to shift the lever when DDC is used than when pushed straight through? Surely the extra effort must be caused by friction and the more friction there is the greater the wear and tear?
Sorry I missed that gardun 
Now where’s the referee 
