Ok.....

HOW does an escort/saff 4x4 transmission send more power to the rear than the front? (correct me if i'm wrong i think its 43/57?)
Anyway, looking at a few pics of transmissions, it looks to me like the gearbox has a (chain driven???) shaft which transfers power to the front diff, and a conventional prop to send power to the arse end. Lets say for a minute thats as complex as it is, would the power be a 50/50 split? I would understand that, as it would just share the power between the axles.
What i dont get is how MORE power goes to the rear when (again, correct me if i'm wrong) it is just a mechanical system ie no centre diff controller or electrical magic etc.

Cheers

 

its the centre vc in the gearbox,

mines 50/50 though.

 

63% rwd as standard i think, but it varies as they get older anyway IME

The thickness of the fluid in the VC effects how much power goes where i believe.


Berny did a great write up on it, but i cant find it now

Stu will probably be able to track it down though

 

VC= Viscious coupling?

 

@ "viscious"
should be viscous (sp) lol

Steve

 

Well on the cossies you might have been right the first time, its not the smoothest system in the world

 

LOL

 

The VC doesn't effect the torque split until wheel spin occurs. The torque split is done using planet gears.

The drive from engine comes to the planet gear carrier (green) which makes the entire assembly rotate. The sun gear (yellow) takes the drive to the rear prop shaft and the annulus (red) drives the chain for the front prop (quite sure it went that way...). The VC is connected to brake any speed differences between the annulus and sun. The ratio of teethcount on the sun/planet/annulus gears dictate the torque split ratio. The smaller the sun gear compared to the planet gears, the less torque goes to the rear.

 

JesseT, thanks for correcting me

 

Thankyou JesseT
Has helped lots. One of them things I could never understand,

 

simple
it sends 1/3 of it's torque to the front wheels and 2/3rd to the rear via the gearing in the transfer box
the vc makes no difference to the torque split under normal driving conditions as it is locked all the time
only when the rear prop starts to turn faster than the front will yo get the torque going to the front prop via the vc and chain afterwards

if you were to remove the front prop the vc would burn out very quickly, in a matter on a mile or so, and then you would be left with no drive at all as all the torque would be being sent through the path of least risistance, ie the front prop, and seeing as it's not there, you won't get any drive going to the rear