hi all. first just got to say great website, very helpful.
now my basic question regarding gears !!
Reading through other posts it seems some hgv`s have a 4 over 4 g/box. could someone explain this to me, is it similar to a hi/lo box in a 4x4 vehicle ? also read about clutching twice while on the downchange. why is this necessary ?
sorry if these questions seem a bit basic but having never been in a truck i dont know. i just want as much advanced info as possible before i start my training.
many thanks, Jon
Artics usually have 12 or 16 forward gears (excluding crawler).
Scania’s :
LOW BOX
X-2
1-3
HIGH BOX
X-5
4-6
Splitter is rocker switch on the front of the stick to split each gear and you lift the collar up at the bottom of the stick to toggle between low and high box. So to go from 3rd to 4th you’d lift the collar up whilst in 3rd, press clutch down, move stick up, left and down to put it back in 1st gear position (now 4th because you’re in high box). There’s no gate where the ‘X’ is.
Volvo’s :
LOW BOX
1-3
2-X
HIGH BOX
4-6
5-X
Pretty much the same as Scania’s but all your gates are back a place, if you follow me. Switch on front of stick to toggle between low and high box and your splitter switch is on the side in the form of a rocker.
DAFs :
LOW BOX
1-3
2-4
HIGH BOX
5-7
6-8
Switches like the Volvo but you’ve got 16 gears on the DAFs whereas only 12 on the Volvo’s and Scania’s.
MANs & ERFs :
Same as DAFs pretty much, but you have have a little switch on the front of the stick which slides left and right for your splits.
Mercs :
Paddle style gearbox. Basically, push the stick forwards to go up the gears and pull in back to go down. Use the paddle on the front for your splits.
Double clutching is used going up through the gears and when up changing you would push the clutch in, select neutral, release clutch, push in again and the selct new gear, release clutch. This gives a smoother change.
Double declutching is used when coming down the gearbox, and basically is the same as above, but when you have selected neutral and lifted the clutch, you rev the engine before pushing the clutch in and selecting the down gear.
This also gives a smoother change and stops the engine ‘grabbing’ gears.
If you are driving an older vehicle with a non synchro or crash box, then this is the only way you can do your gear changes. If you are driving a more modern vehicle it is not necessary, but will give smoother changes once perfected. It is also useful if the gearbox is a bit of a pig and the gears don’t slot in nicely.
I was taught in a Scania with a non synchro 1st, the instructor made us double clutch all of the time so that we could be perfect on the gear change ex.
It came in handy when I had to drive an old ERF one day, the guy out with me reckoned most people couldn’t get the hang of it.
Somewhere on here is a really good post about splitters and range changers, I’ll try and find it and post the link.
Here it is, - from the “Frequently Asked Questions” forum…
trucknetuk.com/phpBB2/viewtopic.php?t=102
Well done Graham, I wondered if someone might find it first.
What a helpful bunch of Graham’s we are!
Graham.
the scania gear stic changed on some models towards the end of the 4 seris and a new gearstick was brought in the range change is on the front of the stick, and the splitter switch is on the passenger side of the of the stickat the top the collor is used to fold the stick flat thought the gear box layout is the same
brilliant. thanks very much , that all sounds reasonably simple,particularly the double clutching. i suppose i can practise getting the jist of that in the car ? guess the rest will come with abit of experience behind the wheel of whatever truck im learning in.
One of the biggest concerns with new starters is the amount of gears and the unfamiliar ways of getting all of them. I learnt on a 5 speed which was great, no range changer to worry about, but got first drive on a nearly new Scania 18t with 4 over 4. Another driver explained how it worked and after a while it was fairly straightforward. The sort of gearboxes you are likely to come up with at first in a training vehicle are going to be straightforward as it is one less thing to worry about. There are some odd ones about but generally common sense will sort out what is going on. Always ask another driver if you are unsure, most of us are helpful and will lend a hand to someone who is not too proud to ask.
Another thing to remember is that if you can’t get it into the gear you want then you are probably trying to get it into the wrong gear.
The nice thing about a four over four is that is it nice and easy to know what gear you are in, which corner of the box and switch position give it away nicely. Imagine have H-H on top of the stick, you’d feel like a signalman on the railway.
dont double clutch a truck with single plate cutch youll knacker the clutch faster
especially on newer truck ie renaults sania etec these trucks and a single plate clutch which is weeker than a double plat cluch
alix776:
dont double clutch a truck with single plate cutch youll knacker the clutch faster
especially on newer truck ie renaults sania etec these trucks and a single plate clutch which is weeker than a double plat cluch
Agreed. It’d have to be a pretty old wagon to necessitate double declutching. All modern motors have synchro boxes in them which means changing gear just like you would in your car.
A little tip for you, if you jump in a wagon and go to put it into reverse from neutral you might find it grates like chuff and won’t go in for 5 seconds or so (the MAN TGAs, ERF ECTs are especially bad for this). Before putting it into reverse, put it into one of the forward gears and then try it - it will then go in without grating. 
I cant think of a truck within the last 15 years where you will need to double declutch.
The ERF was an L reg which is about your 15 year mark. Thankfully nothing like it has been given to me again so haven’t had to faff about doubling except on one 52 Iveco which seemed to be the only way to get the lower 4 gears without the box grinding itself to bits.