Disco 1 Hi-Lo box, Diff and fuel problems linked?

Please bear with me on this thread as I try to explain what has happened......

First off I have a 1995 Discovery 1 automatic. It's a 3.9 v8i petrol with approx 69k on the clock.

Been running it for a few months now but ive never been off road with it. So yesterday, whlist driving on a long quite stretch of road, I decided to engage the Hi-Lo box and diff lock to keep them running. Went into Lo box fine, went into Lo box with diff on no problem too. However, when I went from Lo diff engaged down to Hi box it made an allmighty bang and wouldn't drive. I then took the diff lock off so I was just in standard Hi box mode but it still wouldn't drive. When moved back into Lo box I could continue driving but whenever I went into Hi box and tried to drive I couldnt (just revving when I accelerated)

After a few attempts of moving forward in Lo box then going back into Hi box it finally sorted itself out and I continued home.
Also this morning I went to work, approx 4 miles, with no problems and left the Hi-Lo box and diff alone and thought nothing more of it.

However, after work the car didn't seem to be driving as it usually does, and felt very sluggish. I also burned a lot more fuel then normal!

On average I get 40 miles from every notch on the petrol gauge, so when I left work the needle was bang on the quarter tank mark, but 15 miles later the needle is touching the red empty tank area.

So once back home again I had another play with Hi-Lo box and the diff and I got the same results as last night. Drives fine in Lo but when switching back into Hi box it doesn't engage. Finally after driving a few meters forward in Lo, Hi box engages.

So my two concerns are why have I burnt so much fuel in such short milage and why doesn't Hi box engage first time when coming out of Lo box?

Could it be possible that after first testing the Hi-Lo box last night, ive not fully moved back into Hi box hence why I used so much fuel on a realitivly short trip?

Would it even make a difference to the amount of fuel used travelling in Hi or Lo box or with diff engaged?

Thanks for any help you can give regarding this situation it is much appreciated!!

Without trying to "put you down" in any way, I think you really need to learn what the transfer box, what you call the Hi-Lo box does, likewise the diff-lock.
The low ratio position on the "T-box" gives you what are in effect a number of gears which in effect lower than first gear. I can't comment on the actual gear ratios, but when I engage the low ratio just to periodically check it, running in fourth gear feels like the Disco is running in second. The low ratio gives you a lot of torque couple with lower speed. Normal road running should be done in the High ratio position on the transfer box.
Changing from Hi to Lo through the neutral position can be done on the move but at a speed of no more than 5 mph.
The diff lock (Centre Diff Lock) inhibits the action of the differential gear in the transfer box, effectively locking the front and rear prop shafts together. The CDL is usually used in off-road conditions to help reduce the chance of loss of drive due to wheel-spin.
So far as you're fuel usage is concerned, you're probably getting the same sort of result as you would if you drove to work with your auto-box locked in second gear.
Personally I would say that you've broken something in the transfer box, maybe something like stripped teeth on a gear wheel.
Both the transfer box and the diff lock are "off-road" devices and shouldn't be engaged on a "long quiet stretch of road".

m1dge said:

Went into Lo box fine, went into Lo box with diff on no problem too. However, when I went from Lo diff engaged down to Hi box it made an almighty bang and wouldn't drive.

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Despite what advice regarding engagement of Hi/Lo ratio in the transfer box has already been given, I would recommend that any time low range to high range or vise versa is undertaken the vehicle should always be stationary, and, especially with an auto box, moved to neutral, there is an instruction tag in the cabin of the Disco or refer to your owner/operators manual, engaging Hi/Lo on the move at any speed can cause damage.
Conversely it is ok to make the shift to "Difflock" whilst on the move, (I have done it at speeds up to 100Klm/hr on dirt roads to get better handling stability, back slightly off the accelerator before moving the transfer lever across), with the proviso that the front wheels are straight ahead, i.e. not cornering and that all the wheels are turning at the same rate, DO NOT engage difflock if traction has been broken without backing off to have all wheels at the same rate of rotation.
Try to get hold of a Disco 1 owners/operators manual, the principles of operation for the tranny are all laid out there.

Thanks for the replies guys.

I understand how the diff and Hi-Lo box work and when they are needed. However with me not having the opportunity to use them in such circumstances the other night was just a check to see if everything was running ok/ to stop them sieseing up. When I did switch I was in nutral and stationary. I was never intending to drive on normal conditions in Lo box or with the Diff engaged it was simply a matter of checking everything was working as it should whilst the roads were quite (as I kept stopping to put it in nutral)

So in theory if I did drive in Lo box or with the Diff locked or the transfer box not fully engaged back in Hi position it shouldn't effect the fuel usage?
I don't understand how I used so much fuel in such short milage

Thanks again for the replies and any more advice on the transfer and Diff will certainly be taking on board.

m1dge said:

I don't understand how I used so much fuel in such short milage

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Stopping , starting and use of low range will always increase your fuel usage, the engine is doing lots more revolutions for the distance covered, (miles), than normally done , my 300 tdi will only do about 275 Klm on the top half of a tank of fuel when tooling about town on short hops but on a long run that same quantity of fuel will take me over 450 Klm, it's just how it works, but your Disco may have developed some other problem that would account for the loss.

You should have got a manual diesel then instead of a juice gobbler !!!!!!!!!!!!!!

Magicgrotto said:

You should have got a manual diesel

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It is a manual, still uses fuel.

First off I have a 1995 Discovery 1 automatic. It's a 3.9 v8i petrol with approx 69k on the clock.
Now I've had a drink ! HOW much have you had ???? LOL

m1dge said:

First off I have a 1995 Discovery 1 automatic. It's a 3.9 v8i petrol with approx 69k on the clock.

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Now I've had a drink !! have you ??

Magicgrotto said:

First off I have a 1995 Discovery 1 automatic. It's a 3.9 v8i petrol with approx 69k on the clock.

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I realise all that, just pointing out that even a Diesel lump will chew the fuel when used in stop/start and lo range mode, you were asking a reason for your extra fuel usage, this is one possibility, and we all know the Rover V8 is a heavy drinker!

Magicgrotto said:

Now I've had a drink ! HOW much have you had ???? LOL

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Answer.....no drinking, except coffee, I've just had breakfast, it's Saturday morning here in Ausland!

I know its a thirsty beast it just seemed to use a lot more fuel then normal. I basically do the same runs every day of the week, just this time the gauge seemed to drop in less mile then it normally does.

Will fill up and see how it goes.

Is it perchance still in diff lock , and so getting a bit wound up?

The diff lock and low range is not used ever on most road cars and raley on off roaders, check nothing is jammed in the wrong setting.

freelance said:

so getting a bit wound up?

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Think that's the owner with the amount of fuel it's drinking

Magicgrotto said:

Think that's the owner with the amount of fuel it's drinking

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Haha yes definitely

I've put £20 today (tight b*stard!) So will keep an eye on it and see how we get on.

My mechanic mate came up to have a look last night too and he can't find anything wrong with it. Think I might have another play with the transfer box and diff lock. If something is jammed then hopefully it will un-jam and we'll be back to normal!

Considering your earlier posts, I'm inclined to say that it's stuck in low ratio on the transfer box.

brian47 said:

Considering your earlier posts, I'm inclined to say that it's stuck in low ratio on the transfer box.

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I though that too after the two other posts mentioned it. However, I've driven in Lo box and Hi box again yesterdsy and there is a clear difference in how it drives.

I'm starting to think the transfer box is fine and the problem is coming from another source. It just doesn't seem to be pulling like it used to and feels like the handbrake is always on whilst driving (it isn't I checked that first )

Maybe I'm just been paranoid!

m1dge said:

If something is jammed then hopefully it will un-jam and we'll be back to normal!

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I hate to say it, but I would refer you to the first reply. As this sounds like you don't understand how the diff lock works and what it does.

As for the issues.

I suspect the fuel consumption is a complete red herring. And probably unrelated if an issue at all.

In terms of clonks and the like. If it hasn't been used much in low and diff lock, then the selectors on the transfer box may be sticking, making it hard to select a ratio. Jumping out of a ratio is not uncommon on LT203's either.

I would also advise you jack the vehicle up and check that diff lock has indeed disengaged. Driving on the road with the centre diff locked will only result in stuff breaking.

It is possible that something is binding causing performance issues and poorer mpg. But it's probably unlikely. If there is something engine related, then it is likely it is just coincidence.

It is possible you have a bit of transmission wind up. Jack one the wheels off the floor to release any wind up in the transmission.