I’m sure someone can explain this .retarders why are some stronger than others and are they hard on an engine ,may sound stupid but never got round to discussing them ,I used to drive a daf and used it all the time sometimes during the day I would hardly touch my brakes also water or oil retarders.
Also on a scania could never figure out how to use the ret button on the stalk properly 6or 4series that is, the one with the cruise control on it .
Deeireland:
Also on a scania could never figure out how to use the ret button on the stalk properly 6or 4series that is, the one with the cruise control on it .
thats not a retarder button on the cruise control, all that button does is reduce your set cruise speed when traveling press the button the other way and you accelerate up to limiter speed or how ever far inbetween 
you can use those buttons as well to set idel speed as well if using pto ect
Oh, 
ah well may as ask now I’ve made a plonk of myself what does ret stand for then
Deeireland:
Oh,
it means ■■■■■■ speed 
Ah ok ,can that question be deleted, any thoughts on the first question
I wouldn’t say they are hard on an engine, as if we’re on about the kind I think of, they work on a magnet wrapped around the propshaft?
There are different types of engine brakes,some of them vary the valve operation making your engine into a compressor thus slowing down the vehicle.There is another sort that uses electro-magnets they usually operate on the prop. shaft.
Ta,what about the water ones ?does the new actors have water retarders
Sor
most retarders are oil hydrolic,work the same as a hydrolic pump but just push the oil through a restriction which can be made smaller so requires more force, the oil is then cooled by the trucks radiator like on an auto car.
the older ones can be electronic but they were really heavy and died out i can’t think of any now with them except possible real heavy haulage stuff, that was like a big dynamo working in reverse and was cooled by a big heat sink hence the weight
dew:
I wouldn’t say they are hard on an engine, as if we’re on about the kind I think of, they work on a magnet wrapped around the propshaft?
yes they do, although the most popular place to mount the magnet, in on the gearbox casing… 
That’s what I thought they worked on that hydraulic principle
philgor:
dew:
I wouldn’t say they are hard on an engine, as if we’re on about the kind I think of, they work on a magnet wrapped around the propshaft?yes they do, although the most popular place to mount the magnet, in on the gearbox casing…
You almost had me there, different magnet
From what I remember they are quite heavy so not always favoured on trucks, very popular on coaches though. Good idea
I Always use the retarder ,not on throttle lift off (loose momentum) but on first brake pedal application,the best is Jake brake,(Jacobs engine brake,alters valve timing Yank engines mostly), the Telmar electro-magnetic fitted in drive line is v,good (coachs often have them) but they are heavy for a lorry I belive France&Spain(prehaps before E U ?) made allowances as it was a safety devise
So does the water one work on the same principle as the hydraulic one ?
Deeireland:
So does the water one work on the same principle as the hydraulic one ?
Never come across water retarder but ZF gear boxs can have hydraulic but water cooled,the most simple type is the exhaust brake a gate or butterfly valve in the exhaust system!
Thought I read somewhere the new actros is water ,water cooled?
MAN have (or had) a water retarder
The ZF intarder (avail on most trucks with ZF box (ie DAF, MAN, Iveco) has an empty chamber with an impeller in it. When you apply the Intarder the chamber floods with gearbox oil and the gearbox-driven impeller churns it against a stator.
when the Intarder is released the oil is drained out of the chamber.
engine brakes work by opening the exhaust valve just before TDC on the compression stroke, so the piston doesn’t get ‘bounced’ down again.
Exhaust brakes close a butterfly valve or gate in the exhaust system and increase back pressure.
There’s another one ,intarder,retarder what’s the difference