Manual Hubs install

Saves fuel, more mpg, less emissions.
You are simply not using energy for stirring a front differential full of thick oil when not in use
Well, that's why they sold freewheel hubs for early Land Rovers, but forget the emissions claim, they hadn't thought of that back then. ​​​​​​

I'm going out on a limb here but I'll wager the difference in fuel consumption and wear of having the front rotating assembly double isolated vs being driven either by the ground or engine is so insignificant as to need to be measured in additional tanks of fuel over the entire life of the jimny. What it isn't is enough to make any observable difference over the usage in a month. I suspect it is in reality a hangover from before the adoption of road going permanent 4x4 systems.

My understanding has always been that a differential doesn’t like been driven by the wheels for long periods of time, but the more I think about it I am struggling to see what the problem would be, the wheels and drive shaft will both turn, but there will be no load on it.

So that leaves the transfer box, both front and rear shaft will be turning at the same speed, but only one will be driven, again this isn’t that different to the box in 4wd.

My assumption that you don’t drive the diff from the wheels is probably because most vehicles with a diff have the drive shaft connected to the gearbox and I know that should be avoided.

There will be extra wear and drag by having the front hubs locked but I tend to agree with Lambert the extra fuel will be very small. I lock my hubs when the roads have snow, ice or a mixture of lanes and tarmac, then switch 4wd as required. However, most of the time and on a long journey the hubs are unlocked.

Robin

This is exactly why I came up with the quick and easy "locking the vacuum hubs with a bolt" method. But people would rather spend £100 on old fashioned hubs they have to get out and fiddle with. I swear most people that fit them have no idea what they actually do.

wrote:

Didn't know that.  So what's the point in having hubs that can unlock?  Just to save a bit of wear on the front axle?

 

Yes, it reduces wear, the axle doesn't have any bearings at the CV joint end like a Landrover (but no-one has ever reported a problem with wear.....)
It reduces fuel consumption because you aren't stirring up the oil in the diff and turning all that metal around (bearings or not).

The transfer is designed with synchromesh to give silent engagement and accelerate the drive shafts from stationary to road speed before the hubs pull in, which is quite nice, but it doesn't need to if they are already turning with locked hubs.

I have a vague idea that the early vitara used to have an engagement/disengagement joint in one of the front driveshafts, like some of the Dana axles, which caused massive wear of the gears in the front diff, and they had to be over filled with oil to try and reduce the problem, somewhat the worst of both worlds....



 

wrote:

I'm going out on a limb here but I'll wager the difference in fuel consumption and wear of having the front rotating assembly double isolated vs being driven either by the ground or engine is so insignificant as to need to be measured in additional tanks of fuel over the entire life of the jimny. What it isn't is enough to make any observable difference over the usage in a month. I suspect it is in reality a hangover from before the adoption of road going permanent 4x4 systems.

Your wager is correct, it makes little difference day to day, probably saves a gallon over the life of the vehicle.
But then they fit smart alternators and start stop tech to save fuel. I guess these can't be measured either, but they still do it. As the advert says "every little helps" 

All useful stuff, thanks.  The vac system works at the moment but it makes me feel better about manual hubs if the vac hubs fail. 

my 2 cents here.. my vacuum system failed because of an air leak. When doing the investigation to find it, both pipes on the front axle broke off due to corrosion. So to fix would require me replacing all the metal piping in the front axle section, and I expected, the flexible hoses too. Then I also ran the risk that the pipes leading up into the engine bay were probably needing replacement too. Something I could not do myself. I priced all the parts and they came up more expensive than the free wheel hubs, labour not counted. Of course I still have the risk that the vacuum piping from the front of the vehicle to the engine bay could leak, but then I intend just getting rid of it and blocking the system at the head of the pipes in the engine bay. I am trying to keep the vehicle as standard as possible, but this time I felt the manual hubs were the best "self service" option. Besides, almost all my 4x4s have had them and TBH this has never been an issue for me. Must admit though, all my 4x4 work was in Southern Africa where snow was no consideration for me getting in/out of the trucks... and after owing many different 4x4 vehicles with them fitted, yes I do know what they do!

Replacing the vacuum pipes like for like is awkward but creating an effective vacuum system from scratch is really quick and easy. You just bypass the whole lot with some pvc pipe. Either cable tie it to what's left of the old pipes, or my preference is to re-route them around the engine bay and down the brake hoses so they are out of harm's way. The whole job takes about 30 minutes and the materials needed cost less than £15.
Next time I do one I'll put together a how-to.