4 wheel drive and fuel saving - ? free-wheeling hub?

[bishopval]

I heard that you can get something called a free-wheeling hub which enables the 4wd to either be automatically or manually turned on/off. As my 4wd 2.5l diesel bongo is always in 4wd, i was hoping to save fuel by having one of these fitted.

does anyone know if it is possible to fit this or similar to a bongo? Has anyone had this done? if so what are advantages/disadvantages?

[missfixit70]

Bongos aren't techincally 4wd in the sense you're talking about, not necessary to add such complications, the 2wd & 4wd really aren't any different in consumption.
What figures are you getting & how are you calculating them?

[teenmal]

I heard that you can get something called a free-wheeling hub which enables the 4wd to either be automatically or manually turned on/off. As my 4wd 2.5l diesel bongo is always in 4wd, i was hoping to save fuel by having one of these fitted.

does anyone know if it is possible to fit this or similar to a bongo? Has anyone had this done? if so what are advantages/disadvantages?

Hi,is this what you were thinking about...

http://www.freewheelhubs.co.za/

[francophile1947]

As the difference is about 2mpg, you'll save about 75p every 1000 miles - is it worth it

[nicstrike]

free wheeling hubs are normally used on 4x4's that have selectable 2 or 4 wheel drive. the idea is that they are engaged (either manually or automatically dependant on type) when you are driving in 2 wheel drive to in increse fuel economy & reduce wear , as otherwise , the road wheel's rotation "reverse drives" the hubs/driveshafts/diff/prop assembly. if you disconnect the front wheels from the drivetrain on a permanant 4 wheel drive vehicle (such as bongo's) you are not "disengaging" the 4 wheel drive system and would be unlikely to make any appreciable saving in costs. the main effect would be to loose the security of having all 4 wheels driven.

[dave_aber]

As Kirsty says, freewheeling hubs are a non-starter on a Bongo anyway.

If they freewheeled, then the front axle would slow down, and the VC would sense the shear and drive the axle to keep up - so the driveshafts would be rotating at the same speed as the freewheeling hubs So, even if the hubs were freewheeling you would still be driving 2 UJs, the front diff, 4 CV joints, etc.

(Technically, the front propshaft would be going at rear propshaft speed and the diff would allow the 2 front driveshafts to go at different speeds if friction dictated it regardless of the actual individual hub speeds due to cornering, etc)

Edit : Must learn to type quicker!