Quick question

[frank rabbets]

Blimey, when I tried about 10 shops last year including Halfrauds nobody had any; only 80 grade.

Frank

 

[Roger Fairclough]

I typed in "gear oil EP 90 grade" and even Amazon sell the stuff.

Let your fingers do the work.

Roger

 

[Gav Peter]

Try the oilman on here...

 

[Chris]

I was worried that mine wasn't EP. Quick look at the can today. It's EP

But I have to wonder about the quality. It seems to get very mashed in a very short time. Diff is rebuilt, axle housing cleaned out, oil changed more times than it really needed to be and yet last two 80's seem to have converted the front oil from honey to slurry in a couple of hundred. No, axle grease not getting past the seals. OK confession, it's Planet oil, not made from the dew scraped from the scales of a crystal dragon. Just local motor factor stuff. But I figured that a standard was a standard. No?

Chris

 

[Roger Fairclough]

I was worried that mine wasn't EP. Quick look at the can today. It's EP

But I have to wonder about the quality. It seems to get very mashed in a very short time. Diff is rebuilt, axle housing cleaned out, oil changed more times than it really needed to be and yet last two 80's seem to have converted the front oil from honey to slurry in a couple of hundred. No, axle grease not getting past the seals. OK confession, it's Planet oil, not made from the dew scraped from the scales of a crystal dragon. Just local motor factor stuff. But I figured that a standard was a standard. No?

Chris

Chris, what state is your rear diff oil in?

If it's the same oil as the front, and it's clean, then maybe it is grease contamination. My front diff oil is a grey gooey mush and that is definitely hub grease because I fitted a standard style grease seal and it can't cope with the lateral movement of the drive shaft. If you are running a poor quality EP oil or a non EP oil, then the loading on the teeth would promote rapid wear. Do you have any swarf in the oil?

Roger

 

[Chris]

Well Roger, this seems really to be the front axle only. My white 80 was the same. There's nothing wrong with the seals, they are OEM and in good condition. It does sound like grease contamination, you are right. But I don't know where from. I have actually swabbed out the axle extension housings. I tipped them with the jack and then warmed them up until they were dry inside. I have JW diff components etc etc. It just seems that a couple of hundred miles in, it looks like grey gravy again. No swarf, no. Just the odd tooth

I do wonder if it's cheap oil. Not that any oil is cheap really. Diffs are sweet really no noise or play. No leaking pinions or anything. It's just like the oil is pulverised. Goes in clear, comes out grey.

Chris

 

[Roger Fairclough]

"If you have eliminated all other possibilities, then what remains, must be the answer".

Now I can't be certain I got that word perfect but I can only think of the following reasons for discoloured diff oil.

1)Water---do you have a leak in your vent hose?

2) Heat---are the clearances in the diff to tight?

3) Grease---sorry Chris, but this is still my favourite.

Roger

 

[Chris]

Roger I cannot fault your theory, but I am also minded to believe the evidence 'of my own eyes' you know? Unless there is a clagnut of grease hiding in there, it is NOT getting past the axle seals. If it were there'd be oil in the hubs and they are perfect. There is no evidence of grease in there at all. Diffs don't even get warm and were set up by Jon and run in, in new oil. Breather is sorted. Always sorted. You can't treat a truck like I do and not maintain the breather. I regulalry give my little top hat a jiggle and even blow the pipe through sometimes.

So the answer may be grease - but from where? I'm temted next time I swap it to put some different diff oil in there. Maybe it just doesn't like the Planet stuff. I did have some Fuchs in there but the diff had to coem out before I'd really had chance to drive it. I need my own oil well, I tell you.

Chris

 

[Roger Fairclough]

No problem Chris and as Viv has just said "this is one of those frustrating problems that seems to defy logic"

From my own experience with the same problem, I was not getting cross contamination either, just a flow of grease into the diff. It wasn't until I did some thinking about how the shaft moves laterally and will overcome the ability of a standard automotive seal that I realised where my problem lay but this doesn't affect your problem because you have OE seals.

One point of interest concerns your comment "top hat a jiggle". Does this mean you are using the OE diff breather?

Roger

 

[Chris]

I know what you mean about the shaft going in an out, but when you marr-tack them they don't do that. I also tried one of the seals on the shaft. You know where they wear in the straight ahead position? Well it was still a very good fit. Needed oil to slip them on.

Yes the top hat is original, I just extended the pipe - but have you seen my truck Roger? My breather is probably higher than your bonnet. There is no muck being pulled in there - but I get your thinking. I need a ladder now just to reach the dipstick.

Chris

 

[frank rabbets]

When I drained my front oil at 30,000 from new it was grey. The rear oil was golden. The seal in the end of the front axle tube is a one way seal and stops oil coming out into the swivel hubs. But it does not seal the other way round so grease can get past it slowly especialy as there is no pressure vent in the front swivel hubs.

Frank

 

[Chris]

That's after 30k Frank. I have had 2 80's and haven't covered 10k between them. Some oil changes due to other reasons, have been after a very few miles really and the oil has still looked poor. I have had more new OEM oil seals than hot dinners and the shafts are good. I just cannot see that in these short distances that enough grease would migrate into the axle to turn all that lot into grey yuk.

Chris

 

[frank rabbets]

Unvented hubs Chris. Brakes heat up, pressure in hub builds up then grease pushes past the one way seal. It's either that or magic.

Apart from that I don't know.

Frank

 

[Roger Fairclough]

One last point.

As the hub pivots about it's trunnion bearings, the flat inner face of the CV joint moves in a arc within the inner hub. I reckon that the shaft will move laterally (wobble) side to side and it is this motion that forces open the lip of the seal, thus allowing heated grease to escape into the diff housing. Big Dave obtained some Yankee seals (can't remember the name) that are supposed to be better than OE ones.

My axle can contaminate fresh oil within 100 miles.

Roger

 

[frank rabbets]

Now that's a good point. The shaft should be held by the bush in the axle tube exactly centrally so it cannot move side to side and posibly lift off the seal for a second or two. So a worn bush may be the cause of quicker contamination than a new bush. I cannot remember the exact construction without taking mine apart again. If the inner shaft is held centrally by the outer shaft that goes through the hub then any play, be it wear or poor construction, in the Bir' joint will cause side to side play of the inner shaft.

Frank

 

[Towpack]

The hubs may be unvented but the outer swivel/wiper seal forms a much poorer seal than the inner axle oils seal IMO so any pressure build up due to the hubs heating up is far more likely to be lost past the wiper. JMO

 

[Chris]

TP, you said it as I was thinking it. You know, these seals are really flexi. If you put one on a shaft and wobble the outer around to simulate what you are suggesting, the inner lips of the seal don't distort and create an opening you know. I am sure that the drive shaft DOES move latterally a little and also in and out too, but given that the shaft float is restricted by the diff at one end and the CV circlip and CV outer snap ring, I'd hardly describe the movement as being 'piston' like. The seal fit on the machined area of the shaft is pretty tight you know. You dot' feel it when shoving the shaft in, but try a seal on a shaft in the workshop. I can't see grease getting through there in any volume. If it did open up a gap, why isn't there oil on my swivel too?

There's theory there, I'm not knocking it. I'm just not buying it chaps. I remain to be convinced that my front swivels get pressurised.
Surely air can get down the stub axle tube between the outer wall and the CV shaft too. I know water does. Even with the end cap on

 

[frank rabbets]

There isn't oil in your swivel housings Chris because there is an oil seal. But it only works one way, like a ratchet. OK so fill up with oil to the level plug then do a few hundred miles and check the level. Will it have risen? It is defo grease in the oil.

Frank

 

[Chris]

Sorry Frank still not buying that. The seal only works one way? Really?

Nah. Where is all this grease coming from? I don't plaster CV grease round the seal so somehow it had to jump across a gap and through a seal.

Nah
This seal is only tight one way?

Nah? Have you slipped one on a shaft to see how tight they are?

Nah.

I think this is cheap oil that us being broken down mechanically. I'm not missing grease from my hubs either.

Nah

C

 

[Towpack]

Why would Mr T use or specify an oil seal that lets grease from the hubs contaminate the diff oil? Even if it was 'accepted' that some grease migration is inevitable, surely the scheduled maintenance oil change interval on the front diff would be more frequent than that of the rear and, AFAIK, they're the same at 50K kilometres or 24 months.

The oil in my front diff also turns grey after a while but I'm getting no oil in the hubs after the hub strip/rebuild with new seals around 2 years ago. Prior to that little job there was definately cross contamination with oil in the hubs and grease in the diffs. After the rebuild I did 3 diff oil changes with a budget oil over a short period of around 3-400 miles in an attempt to flush out any remaining grease in the diff/axle casing before a fill with good stuff. I've since done another change and the oil still looked contaminated. The oil in the rear barely changes from new.