Thread: Different 4WD systems

how many types, lets see

part time with manually selected front/rear drive
part time with automatically engaged front/rear drive
full time
electrical independat wheel motors
hydrauilic independant wheel motors
independant mechanical drive per diff (ICE for each axle)
Viscouse coupled
torque slip distributing drive (now thats a funky pricey setup)

Yeah i think thats all the ones ive heard of/seen....

the last one is common in the ass end of off road 6x6 trucks ESP as a cross axle torque splitter Way cool, spin a wheel and the torque is applied to the wheel with traction... something to do with a star shaped driver some interlock fingers and a set of outer running gear or something....the wheel that spins levers off the fingers of the drive side to the wheel thats not or something, way cool to see in action.... If only I could work out how to engineer it into big red..... But shes a bulky item to install.

There is also the system that current Pajeros and maybe some Jeeps use. You have the choice of rwd, fulltime 4wd (centre diff) or locked 4wd drive (centre diff locked). Low range is only available with centre diff locked.

There are many variations on ways to engage disengage drive in part timers too. Free wheeling hubs or not. Disconnecting diffs, etc.

Aren't the new Disco's and Range rovers available with a diff that sends the torque to the wheel with traction?

The Pajeros use, as described, a 2WD/FT4WD/4WD setup with an open centre diff which can also be disconected to give 2wd or alternatively locked. As mentioned, Low range is only available when the centre diff is locked. I don't know what setup of LSD/locking rear diff they currently have - previously they had an LSD with locker as standard on everything bar the base model.

The Subaru's drive system differs depending on whether it's manual or auto, and whether it is turbo (with LSDs) or not.

I don't know of any comparison sites, sorry. But I'm interested if you find one!

The Pajero system got me intrigued with it's options/combination of a centre locking diff and viscous coupling but I couldn't quite work out how it worked - I presume the viscous coupling is the difference between 2WD and 4WD and then the centre diff is 4WDhigh locked or 4WDlow locked, but it seemed to me that with the centre diff locked you are still using/relying on the viscous coupling or is it possible to by-pass this? (I'm definitely technically challenged when it comes to this sort of stuff)

I'll certainly pass on any useful sites I find (if they exist)

Andy

how bout this dave

the other week when i was doing some part time service and i joined a conversation with with our transport supervisor and a couple of truckies and they asked if the reason that i brought my defender was because it was a real 4wd

i replied, i didn't think there were any other real 4wd drives on the market

i than asked why they thought it was a real 4wd, they replied that 110's had drive to all four wheels

i said are you sure, they said yes

i ask where did they do there drivers course, they said school of trucks

i than asked what the vacuum switch on the dash did, they said thats for when you are on the dirt and were told they would be jailed if they drove on the bitumen with it on

there was an army 110 next to where we were standing and i asked them how many wheels would have drive going to them when the vacuum switch in, they said all four wheels

i than asked the transport supervisor if he was under the same impression, he said yes

i said, i bet you a beer that if jacked one wheel of the ground you would not be able to move the defender, they said no way and that it would drive on three wheels and drag the trolley jack

i said are you sure, they said yep its constant 4wd

i jacked up one wheel and asked again what would happen, they all agreed the 110 would drive off

i and selected first gear and they were all amased that only the tyre in the air turned

i than pulled the vacuum switch out and selected first gear and drove the 100 forward a metre or so

they were now convinced that with the centre diff lock engaged all four wheel had drive

i than jacked a front wheel off the ground to show them they only had drive to two wheels with the centre diff locked engaged

they were very happy as they had a better understading of the driveline, i told them to keep there beer and pass on the knowledge

Not quite sure what you're getting at Weeds. Yes, I understand how the system works, but, it is constant 4wd. The system operates with 3 open diffs,which allows slip between all wheels, but while all 4 wheels are on the ground, all 4 wheels are driven. Once the centre diff is locked the front and rear wheels are turning at the same speed, and slip is confined to front or rear.

opps, hope i explained it right ot the boys, i'm no motor mechanic so i didn't want to get into the technical side of things, i was more trying to point out what happens to the drive train when a wheel is lifted or has minimal downward pressure, the boys were at the understanding that all wheels would still drive even if one is hanging in the air

yep reading my post again and its not worded too good