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Final Drive Oil

Urban Surfer

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Urban Surfer

Pardon me, some of this is about oil

Just changed the final drive and transmission oil. The oil in the transmission looks new, but the oil in the final drive looks very dirty, It's been 20,000 kilometers since the transmission was changed, and I believe the same for the final drive, but for certain no longer than that.

No metal flakes in the oil, minor black debris on the magnet. Would it be worth sending the oil in to be tested?

Does any one actually replace bearing and seals after so many miles, or just when they fail?




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Evening Urban Surfer



Always a good idea to get base oil sample testing on things like final drives, transmissions or engines.

But it comes down to cost vs what you will learn. Oil samples on things like final drives work much better IF you have a baseline from a time period just after break-in to compare to.


Due to the way hypoid type drives work there will always be a lot of gear tooth wiping as the gear sets mesh, so fine (non sharp) metallic particles will usually be present at oil change time. That is pretty normal final drive findings.


On the gear oil looking dirty, that kind of comes with final drives or most hypoid gear systems. Partly because of the continuous friction of the gear teeth and partly because some gear oils have a lot of moly type friction modifiers in them. A lot of companies use a fair amount of moly additive on new final drives to protect the gear sets during initial break-in.


One thing I always do is strain the gear oil from both trans and final drive through a coffee filter or common paper towel (it takes a long time due to the oil thickness). Then take the filter or paper towel out in the sun and view it. That will show what is in the gear oil, how shinny it is and how much present.


Don’t forget the final drive on the 1100/1150 has an open venting system so it breathes in air and moisture from heating then cooling off so some dirt and moisture gets in during normal usage.


As long as there are no sharp metal particles in the final drive oil that pretty well indicates the crown bearing is not in immediate danger of destructing. Shinny or sharp metal in the final drive oil is a sure sign of impending doom.



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Yep. I go by the grime on the magnet. I wipe that off with my finger and give it a rub. If it's not at all gritty, you're good. I also capture a little oil in a clear glass container, take it outside and look for anything shiny swirling around in there. Some of the wear items are non-ferrous in the gearbox.

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"... If it's not at all gritty, you're good..."

True, dat. If the oil from the FD looks black, then the previous owner had moly put into the oil at some time.

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