Thread: Front and rear diffs - oil full of metal flake

Originally Posted by DiscoJeffster

I have read a few guides on oil analysis and found that the general consensus is 1000ppm for a differential is the recommended contamination limit, with diesel engines at approximately 80ppm. Transmissions around 200-300ppm.

So if wear was linear, and we used these recommendations, in your case the front diff could be done at around 85,000km and rear around 125,000km (130,000km factory recommendation?)

I should add that this does support everyone’s recommendation to do the front diff more regularly than the factory recommended change interval.

Isn't it better to have 0 parts per million by changing the oil??

Shane, interesting numbers. I'll put my ignorance out here for all to see, but I thought that those sorts of iron concentrations were a bit on the high side? Wouldn't something closer to 100ppm (or at least <200ppm) be a better place to operate? Not my area of detailed knowledge so looking to learn something.

I'd hate to know what mine was. It'll likely be >1000ppm still after the oil change given the metal paste settled in the bottom... Front was a visibly a bit cloudy too, which means the moisture content was way above safe levels.

My 2007 D3 had to have both diffs replaced under warranty (at under 100k), because both went the same way with metal through the oil. So losing both diffs might not be that unusual.
What might be unusual is getting LR to own the problem, and dealers may well ignore it until warranty period finished.
Have heard lots of occasions where LR (or their dealers) have denied a problem to avoid warranty repairs.
Many take their vehicles to RAC or equivalent for a full check before warranty runs out, just to keep dealers honest.

Originally Posted by trout1105

Isn't it better to have 0 parts per million by changing the oil??

Well of course it is, but the point of oil analysis is to understand the level of contamination and viscosity of the oil to determine the optimum time to change to maximise its value. Value being the cost to change and supply new fluid versus the efficacy of the existing product. Knowing the contamination level allows you to make this judgement call. Obviously you can err on the side of caution and replace more frequently or maximise value by managing contamination levels.

You wouldn’t even have zero ppm after a change. One drive and it would be contaminated beyond 0 ppm. Parts are always wearing, the oil suspends the particulates so that it can get caught by the oil filter (rather than settling within the engine as sludge), or in the case of a differential, until it’s caught by the magnet as differentials don’t have filters to capture the suspended contaminants.

Finally, contaminants too small to be trapped by the filter is what is measured by oil analysis.

I would think that as the oil breaks down/degrades and also gets an increased amount of contaminants in the oil it would accelerate the wear on the diff components.
Swapping out a litre or so of oil isn't that expensive and probably less expensive than just having the oil analysed.

Originally Posted by trout1105

I would think that as the oil breaks down/degrades and also gets an increased amount of contaminants in the oil it would accelerate the wear on the diff components.
Swapping out a litre or so of oil isn't that expensive and probably less expensive than just having the oil analysed.

You’re missing the point of ConMon.

It’s about understanding wear, maximising life and value.
It’s also about understanding what type of wear is taking place.

Another “fun” thing to do is send fresh from the bottle oil out to analysis.. it can be an eye opener!

Originally Posted by trout1105

I would think that as the oil breaks down/degrades and also gets an increased amount of contaminants in the oil it would accelerate the wear on the diff components.
Swapping out a litre or so of oil isn't that expensive and probably less expensive than just having the oil analysed.

This is likely true. I made a massive assumption that oil contamination will be linear but you are right that it will exponentially increase as the oil slowly breaks down.

I’ll admit that I am now convinced based on the evidence presented by Shane that the front diff does need more regular changes compared to the rear, and compared to the service interval stated by LR. As has been mentioned, might as well do both at the same time while you’re under there.

I do understand what ConMon is saying But I would much prefer to change the oils in engine, transmission and diffs frequently as a preventative maintenance program, Getting the oil analysed and only changing it when it is on its last legs is unacceptable for me personally.
I am of the belief that changing out the oil BEFORE it starts to degrade or gets contaminated is a much better maintenance regime that waiting until the oil is practically useless and only changing it at that time.
Components running in nice clean oil will always outlive components that have been left to run in substandard oil.