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Transfer Low Range Front diff problems

MarkW

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Aug 20, 2014
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morocco
bad day today. Long low range climb over a mountain. When I went back to H the diff light stayed illuminated and the diff locked.

Tried move through H HL and LL driving in circles and reversing nothing seemed to release it. A few KM further on and I smell burning so stop to see smoke coming out underneath near the front diff.

Popped the bonnet no flames but signs of oil from the front diff breather (extended upto the scuttle panel). Not huge amounts.

Some locals called a mechanic and whilst waiting I started poking about. Nothing obvious but transfer and diff fairly hot. After a while the light went out in the dash and every seemed ok.

Driven another 25km cautiously to the mechanics garage. No more smoke and no noises.

Could the transfer have got stuck locked and caused the front to heat up resulting in oil loss through the breather? Driving it everything seems fine now.

Maybe @BobMurphy has an idea?
 
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bad day today. Long low range climb over a mountain. When I went back to H the diff light stayed illuminated and the diff locked.

Tried move through H HL and LL driving in circles and reversing nothing seemed to release it. A few KM further on and I smell burning so stop to see smoke coming out underneath near the front diff.

Popped the bonnet no flames but signs of oil from the front diff breather (extended upto the scuttle panel). Not huge amounts.

Some locals called a mechanic and whilst waiting I started poking about. Nothing obvious but transfer and diff fairly hot. After a while the light went out in the dash and every seemed ok.

Driven another 25km cautiously to the mechanics garage. No more smoke and no noises.

Could the transfer have got stuck locked and caused the front to heat up resulting in oil loss through the breather? Driving it everything seems fine now.

Maybe @BobMurphy has an idea?

Good morning Mark. Sorry to hear of your problems. Is it your centre diff that stayed locked?

As you have recently had the front diff re-built it could be worth changing its oil and checking that there are no foreign bodies floating around in there anyway.

A while away I know but I can bring bits out from the UK if you need. Good luck :anguished:.
 
It was the rear that was rebuilt Byron, but yes centre diff lock wouldn't disengagethen the smoke and oil discharge from the front diff breather.

Transfer box has always been ok and had fresh oil before I left
 
I once drove for 30km on very soft sand and when we finally got back to the tar we stopped and noticed the smell of burning oil, some smoke (albeit not a lot) and diff oil all over the underside of the vehicle. After umming and arring for a while we couldn't find anything out of place so we drove gingerly to the nearest garage who had a look and couldn't find anything.

The only thing I could come up with at the time was that there had been too much oil in the diff, which had expanded out of the breather and ended up on the exhaust.

That was years ago. Still not sure if i'm correct but never had a problem since. Interesting that you've come up with the same theory. Just some food for thought. Hope you figure it out.
 
well fingers crossed, another thought was heat and altitude.

Off to the garage to find out, fingers crossed
 
Hey Mark! Sounds like nothing wrong to me and I hope it is nothing wrong. Could be more oil in the diff or the transfer case.Could be clogged breather and after getting hot and getting under some pressure the dirt gets out with some oil. The light does that once in awhile, especially when sand and mud are involved. The sensor gets dirty etc. I bet all it needs is some cleaning.
P.S Diffs, gear boxes, transfer cases, engines etc get hot when in motion ;)
 
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Surely you would feel the difference in driving if the centre was actually locked ?

My thinking is a blocked breather has boiled the oil to a point where the pressure has forced the blockage to clear .
 
The Centre Diff Lock light was on so, unless the switch was seized, the diff was locked - the lever just moves a spring, the light tells you what's really happening.

With the diff locked on a solid surface (dry road) there will be "Transmission Wind-Up" as the tyres can't easily slip and release the tension.

This will put a strain on the two axle diffs, the drive shafts/half shafts, the Transfer Box and the clutch/auto box.

It sounds as though the strain has caused your front axle diff to heat up.

If nothing broke and the centre diff is now unlocked you should be OK to continue. Just be aware that the weakest part of the chain is probably the Centre Differential Planet Carrier that can disintegrate when under this kind of load :whistle:.


DSCN5569_zpsnh1v5b6i.jpg


This is what 'Ali' did to his while off-roading :icon-redface:.

Bob.
 
I'm no mechanic, admitted, but I don't see how a locked diff can cause overheating.

If anything, locking a diff would logically give it less work to do, at the expense of adding strain to drive shafts, etc.

But reading the posts more carefully, it seems it was the CDL that was locked and yet the symptoms manifested in the front axle diff.

That's odd to the extent that I would disregard it.

However, I have no explanation as to why the front diff should overheat, as excess oil (if any) would simply spew out of the breather on expansion or in the extreme, boiling. (Boiling point must be pretty hot!).

How can you overfill a diff, usually the filler plug is also the level, so it would just piddle down your forearm.... :think:
 
I'm no mechanic, admitted, but I don't see how a locked diff can cause overheating.

If anything, locking a diff would logically give it less work to do, at the expense of adding strain to drive shafts, etc.

But reading the posts more carefully, it seems it was the CDL that was locked and yet the symptoms manifested in the front axle diff.

That's odd to the extent that I would disregard it.

However, I have no explanation as to why the front diff should overheat, as excess oil (if any) would simply spew out of the breather on expansion or in the extreme, boiling. (Boiling point must be pretty hot!).

How can you overfill a diff, usually the filler plug is also the level, so it would just piddle down your forearm.... :think:

Clive

My understanding is that once the centre diff is locked the front and rear propshafts must rotate at the same rate.

If a car is ascending a winding mountain road the front wheels will often need to turn at a faster rate than the rear wheels as they are covering a greater distance as a curve is negotiated.

Normally the centre diff sorts this (differential) out. With the centre diff locked you are going to get 'wind-up' as Bob has described. This will result in much greater force being applied to all the mating surfaces in the drive system. This increased force will result in temperature rises throughout the drive system and / or system failure. This is particularly the case if the road surface has a good adherence to the tyres making it difficult for the system to relieve the pressure by spinning a wheel .

Though, as you point out, the strain in this situation is on the rear of drive system not the front.

The easiest way to overfill a diff (on an 80 at least) is to add the oil when the car is on a slight incline such that the driver side of the axle is is higher than the passengers. It is amazing how much oil finds its way along the axle with just a few degrees of incline. I found this out by accident but drained the excess oil as soon as I realised what had happened. Though, as it has been pointed out to me, the Collie does not have axle tubes...

Byron
 
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Clive

My understanding is that once the centre diff is locked the front and rear propshafts must rotate at the same rate.

If a car is ascending a winding mountain road the front wheels will often need to turn at a faster rate than the rear wheels as they are covering a greater distance as a curve is negotiated. Normally the centre diff sorts this out. With the centre diff locked you are going to get 'wind-up' as Bob has described. This will result in much greater force being applied to all the mating surfaces in the drive system. This increased force will result in heat and / or system failure.

This is particularly the case if the road surface has a good adherence to the tyres making spinning a wheel more difficult.

Yep, all that makes good sense, but I wouldn't have thought wind-up would be excessive, I suppose the type of track would dictate that.

I always imagine these Morocco trips to be 90% sand/lose driving, but maybe it's not the case.

Like a fool, I once accidentally drove my 80 at 100kph for 1 & 1/2 hrs on asphalt with the CD locked. :wtf:

No noticeable I'll effects whatsoever, I was so worried I went around the truck checking the temperature of the diffs and the tyres, but nothing seemed out of the ordinary.

The main symptom I get with CDL is when turning into my yard gate on full lock, the rear wheels give a skip sometimes.

I've disabled auto CDL in low on the 80, so I can choose to engage, from the dash switch.

I love low-range offroad, with an open diff, I think Shayne puts it down to me being Captain Slow's mentor. :lol:
 
Well after a couple of hours at the garage everything seems ok. They found a melted pipe which may be part of the breather but the language is a bit of an issue.

I've never touched the front diff so it's not bee overfilled. Yesterday was a couple of hours in low range over a mountain and I was aware everything was very hot.

At the moment I think heat, altitude change and a partially blocked breather were the cause.

Both diff and transfer oils are good but engine all was a little low which was a surprise
 
Yep, all that makes good sense, but I wouldn't have thought wind-up would be excessive, I suppose the type of track would dictate that.

I always imagine these Morocco trips to be 90% sand/lose driving, but maybe it's not the case.

Like a fool, I once accidentally drove my 80 at 100kph for 1 & 1/2 hrs on asphalt with the CD locked. :wtf:

No noticeable I'll effects whatsoever, I was so worried I went around the truck checking the temperature of the diffs and the tyres, but nothing seemed out of the ordinary.

The main symptom I get with CDL is when turning into my yard gate on full lock, the rear wheels give a skip sometimes.

I've disabled auto CDL in low on the 80, so I can choose to engage, from the dash switch.

I love low-range offroad, with an open diff, I think Shayne puts it down to me being Captain Slow's mentor. :lol:

Hi Clive

I though that until I arrived there :grin:. Then I discovered that much (if not most) of the desert in Morocco is stone. There is of course sand but most of the time you are bouncing across a hard unyielding surface.

As Mark was ascending a mountain the road is most likely to have been packed stone or tar I would think.

Glad to hear your accidental diff lock caused you no problems :sunglasses:. when you are driving in a straight line the wind-up would be minimal, its tight bends (like turning into your yard) that really crank it up.

Like you, I have fitted a CDL switch so that I can engage low range and keep the diff open. I find that arrangement particularly useful for executing slow tight manoeuvres and driving on soft sand.

Byron.
 
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I love low-range offroad, with an open diff, I think Shayne puts it down to me being Captain Slow's mentor. :lol:

You have led boots and we both know it mate :lol: i don't think we ever did slow your low revving motor just makes it difficult to match gearing/speed to my high revving motor , low box 3rd in mine i think puts us on par but of course i have to lock the centre diff to get it :icon-rolleyes:

Blocked breather equals pressure cooker and they do get quite warm .
 
Well after a couple of hours at the garage everything seems ok. They found a melted pipe which may be part of the breather but the language is a bit of an issue.

I've never touched the front diff so it's not bee overfilled. Yesterday was a couple of hours in low range over a mountain and I was aware everything was very hot.

At the moment I think heat, altitude change and a partially blocked breather were the cause.

Both diff and transfer oils are good but engine all was a little low which was a surprise

Sounds hopeful :thumbup:
 
The Centre Diff Lock light was on so, unless the switch was seized, the diff was locked - the lever just moves a spring, the light tells you what's really happening.

With the diff locked on a solid surface (dry road) there will be "Transmission Wind-Up" as the tyres can't easily slip and release the tension.

This will put a strain on the two axle diffs, the drive shafts/half shafts, the Transfer Box and the clutch/auto box.

It sounds as though the strain has caused your front axle diff to heat up.

If nothing broke and the centre diff is now unlocked you should be OK to continue. Just be aware that the weakest part of the chain is probably the Centre Differential Planet Carrier that can disintegrate when under this kind of load :whistle:.


View attachment 123856

This is what 'Ali' did to his while off-roading :icon-redface:.

Bob.
I reckon thats a spot on diagnosis, they do stick on, mine ( the D4D) stuck on at the weekend after I'd moved the lever to clean round the gaiter and when I put it back to H the bloody CDL was stick on. Several times round the yard in figs of 8 didn't release it but the black lines on the concrete showed how much "wind up" occurs.. It didn't come off so I left it to the next day and thought I'd take it round the village. As i dropped of the kerb onto the road the light went out a d the CDL was released and has released every time I've tried it since.
I'd say the front diff got hot due to wind up but probably no harm has been done.
 
How can you overfill a diff, usually the filler plug is also the level, so it would just piddle down your forearm.... :think:

I always overfill both diffs with extra 150ml. front and 200ml. rear. Lift a bit the back and overfill the front and then lift the front and overfill the rear. The reason I do that is if you read the manual you'll see different oils for different regions. I use 75/90 always and the overfill gives smoother performance when climbing high mountains with rough bumpy terrain in warm weather regions.
Same thing with the engine, always 10 ltrs. of engine oil. Thats ~ 350-500ml more oil. That way I'm sure oil runs through oil pump alway when offroading. For everyday use and driving on asphalt you dont need that much of oil in the diffs or the engine.
 
Well after a couple of hours at the garage everything seems ok. They found a melted pipe which may be part of the breather but the language is a bit of an issue.

I've never touched the front diff so it's not bee overfilled. Yesterday was a couple of hours in low range over a mountain and I was aware everything was very hot.

At the moment I think heat, altitude change and a partially blocked breather were the cause.

Both diff and transfer oils are good but engine all was a little low which was a surprise
 
Not sure why the same post appeared twice but never mind.

Back on the road again and I've gone straight to Zagora to see Ali. Covered about 300km everything ok no more smoke or all leaks. Not used low range today at all.
 
Good to know everything's intact!:)
See you soon!
 
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