Mitsubishi Delica Owners Club UK™

[jejoenje]

okay so I'm pretty worried I have found a more serious problem.

In the process of raising the rear end of the truck yesterday to replace the droplinks, I noticed that the underside of the rear diff housing was wet with oil...  
Left a bit of cardboard under it overnight, and there were indeed a good few drops on the cardboard - so its not just weeping, I guess it really is leaking.   No other adverse symptoms at all yet, no strange noises from the back end, truck drives great as before.

Although I'm at a loss as to how and why but I am now very worried I managed to damage the diff housing with the jack...     Is that even possible?? All the literature I've seen says that that is the proper jacking point, I've only had to raise it maybe twice, and I've always only used it to raise it and immediately dropped it onto axle stands.

Any thoughts anyone, or tips on how to confirm exactly where the leak is, or generally how to proceed? I'm obviously very keen to ensure I am not going to cause (further?) damage.
Are there any common points these diffs would develop slow leaks?

PS. The good news is, changing the drop links has stopped the knocking noises that were troubling me.

[Google]

[Lewis]

The underneath of the diff is indeed a safe jacking point.

Check the connection to the rear of the universal joint.  There is an easily replaced seal inside it.


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[andyman]

What Lewis said, I'd bet. Clean as much of the oil off as possible, use petrol or other cleaner to get it off, especially around the prop shaft seal. Then leave to stand, so you can see ( hopefully) where it comes from. Bear in mind, it will not leak cold and static, as much as it does hot and under pressure from being driven. Do you know if it is a limited slip diff? If so, make sure you top up or refill with the correct oil.Check for play in the prop shaft/diff bearing and the universal joints while you are under there. Don't worry about backlash in the diff gearing, it can seem excessive, as you twist the prop shaft to and fro, but it rarely is! And don't confuse it with worn universal joints, which should be thoroughly greased with a grease gun.
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Andy C L300 Super Exceed - over 100 smiles per gallon!

[jejoenje]

Thanks for the thoughts folks - I'm glad that the immediate response wasn't "jeez mate, you've trashed that!!".  

Interesting - I did wonder about seals, including the propshaft one.
The one thing about this suggestion is that on first investigation it seems to be leaking from the front of the diff housing, but from the very bottom. Although I guess that is where a slow leak might accumulate, plus although I've wiped things I have yet to do a really thorough wipe-down as you suggest Andy. I will do so as soon as I can - hopefully tomorrow.

Partly the reason I got really worried about possibly the jack having caused some damage is that a bit of hardened underseal (at least I presume that's what it is) chipped off the bottom edge. You can see it along the bottom right edge of the diff here:


When I cleaned it off this afternoon and checked a bit later that particular spot seemed a bit oily again.
Also, as I was saying earlier, the other side (front) of the housing seems to be relatively free of oil, particularly towards the propshaft area (sorry crappy photo this one):

[jejoenje]

So kept an eye on the leak last week and had a tub under the truck while I was away over the weekend as well. There definitely is a (dripping) leak but relatively slow. This shows the amount over five days:


I have now also cleaned the underside of the diff with some Gunk, a brush and some paper towels and had a very close look over the whole thing beforehand. It appears there definitely is a leak around the pinion seal as you clever folks already suspected:


However, there is definitely collecting oil at the lowest point of the diff (below which I had the tub):


Interestingly however, when spraying on the Gunk, this is where most of the trips collected in the first place, so perhaps it really is just the pinion seal causing the problem.

My father in law suggested that perhaps the jacking on the diff has caused a slow leak on the (perhaps already weakened) seal, which would explain why I started noticing the leak after I'd been working on the truck a couple of times. Does that make sense?

Now, replacing the pinion seal. I've been reading up on this and it seems relatively straightforward... Most if not all references I can find to it online seem to refer to doing the job on L400's however,
for example Lewis' excellent walkthrough here.
Would anyone be able to advise whether the process is the same, or how it would be different, on an L300?
Do I need to worry about the bearing pre-load for the flange (i.e. count number of turns) in the case of an L300?
I couldn't find any details on the procedure in the workshop manual.

[jejoenje]

Oh, and can anyone confirm that the part number I am looking for is  MB160949 or MR580530?
Reason I ask is that this is what I found in the parts catalog but the latter number is the same as the one for the L400 as shown by Lewis in the post linked above... So is it the same for an L300? I don't fancy taking it all apart and finding the replacement doesn't fit!  

[Lewis]

Oil seal part number MB160949 has been replaced by MR580530. It is also used on the L200, Shogun and Canter trucks

The method is the same for both diffs, as shown in my how to post, including the pre-load info.

HTH  :D
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Copyright is retained for all my photos. Please don't copy them without asking permission
Do not blindly go where the path may lead you. Go where there is no path and leave a trail that others may follow!
ルイス

[jejoenje]

That indeed does help! Thanks very much. Will be cracking on with this as soon as I can and report back.

[jejoenje]

So although I've ordered a replacement seal I've not yet got round to actually fitting it.
However, I have been repeatedly cleaning and wiping any drips appearing to attempt to confirm where things are coming from, and I'm now no longer sure I'm convinced it is the pinion seal that is causing the problem!
As I said, drips are collecting at the very bottom of the bell housing, even quite quickly after cleaning the whole lot up with degreaser and wiping it down. Within a couple of hours, a hanging drip of oil has formed at the lowest point of the diff, just by where I pointed out the cracked plastic underseal in the photo above. Thing is, the rest of the diff, including the area towards the pinion seal, as well as around it, remains dry (and clean) as a bone - wiping your finger along even the seal area comes out clean.

Does this still sound like a leaky pinion seal? I realise any slow leaks from the pinion seal would collect at the bottom point of the diff rather than (necessarily) drip straight down, but I would have thought that would have meant the whole of the underside of the diff (between the lowest point and the propshaft) would have oil on it?

On the one hand I think I'd be happy to just stick a new pinion seal in (although I don't own a gear puller for getting the flange off!) and see what that does, but on the other I don't really want to take stuff apart I don't really have to...

Any further thoughts?

[Lewis]

If it isn't the pinion seal then that leaves either the drain plug, fill plug or worse scenario is micro holes in the casing.  
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Copyright is retained for all my photos. Please don't copy them without asking permission
Do not blindly go where the path may lead you. Go where there is no path and leave a trail that others may follow!
ルイス

[jejoenje]

Mmh.
90% sure it's neither of the plugs - I checked and cleaned the area around both of them as well while topping up with some fresh oil (just to make sure it wasn't running empty).
Is there a seal in between the axle side of the housing and the propshaft side, that could be replaced?

I must admit, perhaps somewhat unreasonably I've got a bad feeling about this, partly because of what I said about a bit of the undersealing "pinging" off while jacking up, and that being exactly the area I've started noticing the drops forming... Perhaps I should just cover the whole thing in more underseal...  :?

[Lewis]

You replied whilst I was searching for an appropriate photo from my collection. Unfortunately when using the iPad Photobucket App my browser occasionally logs me off the website if I take too long.

There is a seal where the diff is bolted to the axle, however it is a RTV type mastic sealant, as opposed to a gasket. You may be able to lift it enough to get some sealant in, but to do it right you will need to pull the halfshafts out to get the diff off:-



This photo is from when I helped Strangerover replace his standard diff with an airlocking one, several years back.

One thing I would suggest is that you get all that cruddy bitumen stuff off the axle, all it does is retain water inside it.
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Copyright is retained for all my photos. Please don't copy them without asking permission
Do not blindly go where the path may lead you. Go where there is no path and leave a trail that others may follow!
ルイス

[andyman]

From your photos, the thick underseal/bitumen appears only to be on the rear 'dome' of the axle/ diff housing. It may be that someone has previously tried to cure the leak in this way. As Lewis says, you'll need to chip it all off, and use  a flexible disc to grind the surface clean. If indeed oil is coming from this area, you should be able to isolate it. If it is indeed a pinhole or a crack, it should be possible to plug or weld it, after first draining the oil.
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Andy C L300 Super Exceed - over 100 smiles per gallon!

[Deker]

Could possibly be that the pressed steel cover at the back has got the holey red disease.

As Andy said = "As Lewis says, you'll need to chip it all off, and use  a flexible disc to grind the surface clean"

If the cover does have rust holes, do NOT attempt to cure/treat the problem with the cover on - Remove it.

Plus - If the cover does have holes, then grinding while it is ON, may send nasties into the diff housing.

Mr D

[jejoenje]

Ugh... This all sounds fun on a Sunday night...

So silly me had assumed that the "black stuff" was just the last of underseal left, but as suggested, it may be more plausible it was actually put on the back of the diff only (well spotted Andy!) for a very good reason!  :? After all it would seem silly to underseal just the back part of the diff and not the rest of it, let alone the axle!

Mmh. I will have to have a careful think about how to proceed. I'd be quite keen to get the black stuff off altogether (angle grinder was a xmas pressie so that will come in handy!) but if there really is a bigger problem as you point out Deker, I might well cause more damage thereby rendering the truck undriveable - given that I can neither weld nor have an (obvious) off-road place to park it, that would be a wee bit of an issue.   :?

Anyway, Deker, the back cover you refer to - I was under the impression the whole of the back of the axle (including the domed rear end that the diff sits in) is a single piece of steel? I didn't think the back of the differential would be removable?

[andyman]

If it is a shrink or press fitted separate piece, that joint is another possible suspect. I suspect it would be very difficult to get it off without damage. Pinholes or small splits NOT caused by flaking rust and massive thinning of the steel, should be repairable with an electric arc or mig welder without causing distortion or weakrning of the steel, and should have no effect on  the rest of the axle/diff, unless at the edge of the cover.
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Andy C L300 Super Exceed - over 100 smiles per gallon!

[Deker]

[Lewis]

[andyman]

Just checked mine, VERY rusty, but definitely not a separate dome, and cast with main diff casing, - the apparent joint line is probably a flashing line from the mould joint
Chip off the black stuff with an old chisel or flat screwdriver, and  use  a  flexible, open mesh type grinding disc ( you may need a couple) to clean off any rust.
You will not grind through the metal, it is far thicker than a steel pressing would be, but pinholes are not uncommon in castings, but can easily be welded over by anyone with experience of welding cast iron, but must be above oil level. Mine has an illegible, metallic sticker above the filler plug, and just wondering if it confirms that I have a L S diff, or should it just tell me what oil to use?
_________________
Andy C L300 Super Exceed - over 100 smiles per gallon!

[jejoenje]

Thanks very much for this all.
Yes, sorry, I was thinking of the grinder to clean up the metal underneath, not the plastic! I figure that apart from an 'orrible mess it would also fling bits of hard plastic everywhere!   Chisel it is! I wonder if carefully heating up the plastic will make it easier to get off... I will get on with this as soon as I have some contingency plans in place, in case it temporarily makes the leaking a lot worse...
Perhaps that back joint is the best candidate for the leak - it is pretty much exactly around where the oil seems to collect the quickest. I know nothing about welding really - so if I understand correctly, it should be possible to weld over that joint?