4x4 front wheel drive not working

[Bob]

I recon you would be best with 4 chains on a 4x4 Bongo as the front wheels will only be driven once a rear one is slipping.

Lidl are doing them soon.

[Dodgey]

Lidl are doing them right now.

I've used chains a lot in the past, and I never want to have to put 4 on! - They are meant for emergencies and doing just two in the snow is a nightmare, especially in the dark.

I agree that 4 would be best but if the front diff only gets power if the rears slip then I'll put them on the back and forgo the steering benefit.

I'm curious to know exactly how the system works because I can sometimes hear the fronts scrabbling when slowly turning on full lock - i.e. parking.

[Dodgey]

Just seen it described perfectly by Dave Aber. (I'm going to put mine on the rears, though theoretically, the fronts should work too)

"Put simply -

The Bongo 4WD is primarily a rear wheel drive layout.

The engine turns the transmission, and the transmission turns the rear propshaft, and that turns the rear diff which turns the rear wheels.

The vehicle moves along the road.

The road turns the front wheels

The front wheels turn the front diff, which in turn turns the front propshaft, which is connected back to the transmission.

Now, where the front propshaft is connected to the transmission is a viscous coupling. As long as the front propshaft is turning (pushed round by the front wheels) at pretty much the same speed as the rear propshaft (turned by the engine) then the VC does nothing. The Bongo is to all intents and purposes a rear wheel drive vehicle.

So, if the rear wheels slip and thus don't push the vehicle along by as much as they should, then the front wheels will be pushed along less, and the VC will see a difference in speed between the rear propshaft and the front propshaft. In this case, the fluid in there which is very clever will be said to be 'in shear' and will resist this difference in speed. This will have the effect of driving the front propshaft at the same (or close to) speed as the rear one, which will in turn drive the front wheels. The Bongo is now 4WD or AWD.

This locking action of the VC happens very quickly, in a fraction of a revolution. So, you could say that it is always ready to drive the front wheels and does so when required 'instantly'.

With any 4WD system, if you have open diffs on both front and rear axles, then it is possible to become stuck if you lose drive on one front wheel and one rear wheel. Either both lefts, both rights or one of each, diagonally. This is true of early land rovers, jeeps, etc. As long as the front and rear propshaft speeds are the same speed one front and one rear wheel can spin happily on snow / mud / ice / whatever and that's you stuck. That's just how it is with open / normal diffs.

If you have a limited slip diff however, the situation is much improved. This limits the speed difference possible between wheels on the same axle. So, for the Bongo where a LSD is an option on the rear axle if you spin a rear wheel on something loose you will also keep drive going to the other side which will hopefully have more traction. At the same time, the centre VC will match then propshaft speeds of the front and rear props. The only way to get stuck now is to have both rear wheels spinning, and one front also spinning. Unfortunately, they didn't do a front LSD.

My experience with a 4WD Bongo with no LSD is that you can quite easily get stuck if you are not careful, or if you are trying to (to see how easy it is) in snow & ice etc, but it is also very capable of not getting stuck as long as you understand the limitations of what you have got. It's certainly less likely to get stuck in mud than a 2WD one in difficult conditions. Audi's Quattro system in comparison uses 3 'torsen' style diffs which all work similar to a limited slip one - with this layout you only need one wheel on firm ground to keep on going.

For campsites in 'normal' weather though? Not a lot in it I'd have thought."

[cavey]

Super explanation Dodgey, thanks.

Now, without finding some mud or ice, how do I check if I have an LSD? Which serial number do I put into which website?

Cheers.

[Bob]

Superbly worded, thanks.

[briwy]

Super explanation Dodgey, thanks.

Now, without finding some mud or ice, how do I check if I have an LSD? Which serial number do I put into which website?

Cheers.

It is this site but it seems to be down at the moment. It's the VIN that you need to put in.

http://www.ruzip.ru/eumz/eumzcat.aspx

If you have a LSD then there is a sticker on the rear diff, difficult to see if dirty, impossible if its been covered in underseal or it may just have come off. Later ones seem more likely to have one I think. Or, at the rear jack up one side, turn the wheel by hand, if it turns freely then likely no LSD, if its stiff then could be an LSD (or could be knackered diff, diff oil should checked)
ps, don't have the engine running.

[New Forest Terrier]

If you have limited slip you can feel it on rough ground or mud. The rear wheels scrabble just like a proper four wheel drive. Mine is a petrol 95 so 2wd + LSD. Not sure if you could identify it so easily on an actual 4wd Bongo though. Mine is brilliant in mud but not good in snow.

Where I thought it should be good, reversing up my steep drive in snow, it is absolutely useless. It just loses traction even before the steepest bit. Brilliant in mud though and I have managed to turn it and get out from a rutted bog I accidentally got directed into on a Forestry Commission camping site. I thought nothing would get out of that but a Land Rover, but with a bit of tactics the Bongo made it.

[Dodgey]

Thanks guys but it's not my words - I copied and pasted from Dave Aber.

Interesting about the rears scrabbling for grip. My Bongo Vin tells me I don't have an LSD but I certainly hear scrabbling when I do full lock turns (I'm an ex 4x4 competitor so I know well what tyre scrabbling sounds like). I've always assumed the scrabbling was the fronts, but reading the description of the transmission system, they shouldn't be doing that at very low (parking) speeds. Perhaps I have an LSD but it's not logged properly. I'll have to check!

Saying that.... a full lock turn will turn the rears (well, outside rear) a lot slower than the fronts. Perhaps it is the 4x4 kicking in.

[hijimhere]

the series ll lla and lll come with an "option". The option is a manual lock on the center of each front wheel - one the locks are turned and engaged the front differential is locked - giving you 3 wheel drive - example when of roading in mud if you get stuck engage the manual locks - result both front wheels are lock in to the same rotation. It seems you do not know of the front axle option. Can only suggest when you are out and about and see any series have a look at the center of the front hub. There are two types freewheeling hubs and locking hubs. If you see a recess with a bar across the center and on the edge the word "lock" with an arrow pointing in a circular motion you are observing front diff lock mechanism. Hope this helps.

[Northern Bongolow]

Super explanation Dodgey, thanks.

Now, without finding some mud or ice, how do I check if I have an LSD? Which serial number do I put into which website?

Cheers.

to check for a lsd jack up both back wheels, spin one by hand, if the opposite back wheel spins the other way its a standard diff, if it spins the same way its a lsd.

[al & chris]

Do bear in mind that although the stickers say Full Time 4WD this is not actually the case.

The viscous coupling on the gearbox detects a rear wheel loosing traction then applies some of the drive to the front wheels as required, they're not actually driven all the time.

This sounds right to me as when on full lock at low speed in snow bongo is still pushed forwards not turning correctly.

[helen&tony]

Hi
'Fraid Landrovers of the series variety weren't that sophisticated...no locking diffs, as they weren't necessary if you look where you're going off-road...The lock mechanisms on the front hubs were all freewheeling hubs, and there were a few firms offering them...Landrover never did.
The reason for the locking hubs was Landrover's incredibly bad reputation for fuel consumption, and as everything on a Landy was massive, the front diffs had a large quantity of oil, a BIG set of Diff gears, large halfshafts, and bearings, all adding to resistance when 4x4 wasn't selected, and by disconnecting the lot at the hub by hub locks, it saved a lot of fuel (theoretically)....I think it only made a bit of difference, but I have fitted Fairey freewheeling hubs when I had one without, and I fitted Fairey overdrive units where there wasn't one fitted...They fit on the back of the box where the PTO is driven.
To look at a "Series" Landy, the hub locks on the front are just that, and not diff locks, as Landrovers had a nasty habit of shearing halfshafts if you push it, so locking a diff would be REALLY bad, unless you fitted highly uprated halfshafts.
In 2 wheel drive, it was usually the rear halfshafts going, so I usually opted for LWB Landies from preference, as they had a Salisbury diff and meatier halfshafts.
Looking inside the cab, a Series Landy has 3 control levers on the floor, Gearlever , High and low ratio selector lever and a short lever to select 4x4. When fitted with a Fairey Overdrive, there is a fourth lever, and it's really fun playing with the gears...but entirely a time-waster, as you only want the overdrive to save fuel...not that it's an incredible saver....
I have had Series 3 and 2 LWB Safaris (all my Series Landies were Safaris, and I regret never having a Series 1 Safari, but then they are VERY rare)...Best drive was a 2.6, six cylinder LWB version....and I was really lucky with fuel consumption....20 MPG on a run, and 15 elsewhere....but great fun...and that's with O/D and FWH
Just looked at the old service schedule, as I still have the handbook.....I remember taking days working on it for annual service ....couldn't afford dealer prices!
Just as Muz said, few 4x4s have full diff - locking...although some have lockable centre diffs...Mercs G-Wagen , and Unimog! have all lockable diffs....I hunted around for a while here to find a nice G-Wagen, but bought a Jeep KJ with LSD instead, after looking at Defenders and others...
Bongo is alright in snow, but limited to around a foot, but it's easy to stop. I've had the Bongo in snow up a mountain track with a caravan on tow....didn't expect to make it...but it did!....
Cheers
Helen

[Dodgey]

Aye - having a freewheeling hub mechanism that could actually lock the diff would be incredible - you'd need hollow prop shafts to allow for the "mechanism" to run through them. Hollow prop shafts on a Landy would last about 1 minute

We always switched the hubs on ours to free-wheel to reduce the transmission whine

[mikeWalsall]

I always thought the Safari roof a clever idea .. be OK on a Bongo ..!!

[helen&tony]

Hi Dodgey...
A MINUTE ....that's being a bit optimistic
That's why I liked the LWB / Salisbury diff ....never had any trouble,,,,even with a socking great Perkins engine in one of my LWBs...now THAT had some grunt
Cheers
Helen