Free Wheeling Hubs.

Those funny things fitted to the front wheels of some 4X4s - by Mick Farmer -Training Director - On Course Uganda

Back to my early days in Uganda and the Toyota Land Cruiser that I was driving and if you read the last issue you know what happened to that.

The organisation I was working for was transporting building materials to refugee settlement in West Nile. The roads were bad especially as it was the rainy season. Why is it that this always happens with NGOs working up-country? They always seem to want things done in the rainy season!!

Anyway, one day I decided to go out and take a look at how things were going. Driving down a particularly bad stretch of road I found myself entering a nasty bit of mud. It got deeper as I went on and eventually the Cruiser got stuck. I was in 2wd! I decided to engage the 4wd and try to get out. But still only the rear wheels were turning. How could this be as the 4wd light was on. I then remembered the funny things on the front wheels and at that moment worked out what they were for. I got out of the vehicle and into the mud and sank up to my knees. I scraped away at the mud around the front wheels and managed to get both into the locked position. I got back into the cruiser trying not to get the inside too dirty. Decided to take off my boots as my bare feet stood less chance of slipping off the pedals. I then put the vehicle into gear and low and behold we started moving and eventually got out.

When I got back to my base I decided to ask around to see if anyone could give me some advice on what these things actually do. After getting some answers like, “They engage the 4wd” or, “They lock the front differential” and, “ They make the vehicle steady”, I got an answer that finally made sense. As follows:

What they do is engage and disengage the half shaft or drive shaft from the hub of the wheel.

When the device is in the locked position the shaft is engaged and when in the free position it is disengaged.

“Why would you want to do this and why do some vehicle manufacturers fit them as standard?” I asked.

In theory when you have the hubs in the free position and the vehicle in 2wd it takes less force to move the vehicle over the ground because the front wheels are only being pushed around and not the rest of the front half of the drive train. Also in theory you are supposed to get less tyre wear because you are decreasing the drag on the front wheels and decreased wear on the moving parts in the front drive train. Since then I’ve always driven a vehicle fitted with free wheeling hubs with them in the locked position and in my experience, it doesn’t really make a lot of difference.

In fact, if you read through the manufacturer’s handbook they will tell you to engage it to the lock position and drive the vehicle around. This should be done every month to ensure adequate splash lubrication to the moving parts to ensure that they do not wear out prematurely!

There is a difference in fuel consumption but it is negligible especially with a diesel engine. On trip say from Kampala to Nairobi (650kms) you might save in the region of about 5 litres.

As to the wear and tear aspect I’ve seen more damage caused by vehicles run in the free position than to the same model vehicle with the hubs permanently locked!

These days some aid organisations order their vehicles with the hubs permanently locked to reduce the risk of damage by operator misunderstanding or “mechanic” misunderstanding!

As you might know from a previous article, I used to drive a series II Land Rover with a petrol engine, called Katie. She had free wheeling hubs fitted by the previous owner. She was driven through some pretty bad environments and I decided to put the locks on full time. (Sick and tired of getting out of the vehicle every time I wanted to put the vehicle into 4wd) Even with a gas guzzling petrol engine, if the Katie was driven with care and respect the fuel difference was negligible.

Just to recap then. If you do run with your hubs free you have to lock them before you select 4wd.

Do not run one in free and one in lock. It’s also a good idea to check them regularly to ensure that they haven’t been tampered with them! This could be costly.

In the end it’s up to personal preference and therefore the debate on whether to run in free or lock will go on till all 4x4 vehicles are full time 4wd. Until then safe and happy motoring.