It is being held back - you have the retarder on… 
Just leave it up.
oneillmartin:
Sound but if the retarder lever is left down like at stage 5 when driving it seems like the trucks been held back I think
Lol well that’s like driving with the brakes on in it!!!
I know yah and what is the button on top of the retarder for again
White Smoke reducer is also meant to be used when you do a lot of idling to keep the engine temps more suitable. But don’t leave it on all the time since it will use a lot more fuel activated.
Top one only works when you are voting for a new pope.
Hope this helps 
I’ve found this quite interesting, I am responsible for Displays and Controls at JCB and to be honest it’s a nightmare trying to make images/icons representative of the function they are intended for while complying with ISO standards.
Shows even the big boys with larger design teams and resources than us struggle.
I hate Japanese cars with all their text on the switchgear, abysmal.
No I meant the button on top of the retarder lever
So to elucidate, you only pull the retarder leaver down when you want additional breaking power & turn it all the way off when you have finished breaking.
oneillmartin:
No I meant the button on top of the retarder lever
Need a picture, I sold mine a couple of year ago, I think it’s the auto or manual gear change button though, so if it’s in A it will change gear on its own but in M it will need you to pull the lever toward you or away from you to change gear.
The top one is a white smoke inhibitor. Should be used when engine is running for long periods on very low revs. It put the exhaust brake on a little to make the engine work harder and stay warm otherwise the electronic fuel device reverts back to thinking it should be on cold start. Then when you put revs on its puts white smoke out…it stops this from happening. Eg long slow moving traffic. Flick it on. Keeps engine temp up. Saves fuel. Other button is the automatic exhaust brake. Just puts exhaust brake on when foot brake is applied. Unless the scania has a gearbox retarder then the retarder does it for you and the switch is redundant
I leave the retarder on auto. Its called Brake Blending according to Scania. When you initially press the brakes it applies the wheel brakes, then brings in the retarder and reduces the wheel brakes, saves massively on brake wear. The retarder is an area where in my experience Scania is unbeaten, its amazing. The engine brake on my current Volvo is rubbish in comparison
The retarder button on lever only works in auto mode flick into auto on switch. The button on the lever is to set the max speed you want to go down hills so drive to say 45 mph press the button…after you do this the retarder will automatically slow you down to 45 mph every time you take your foot off the gas pedal. If the system is working right
Top one is cold weather warm up it puts the exhaust break on a little to put a load on the engine sobit warms up faster don’t drive for long periods with it turned on you’ll hear the engine note change if its on.
The bottom one is for the exhaust brake in aut mode it applies the exhaust brake on the gentle press of the brake pedal on off postion it does nothing
I think he’s got it 