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how does this gear oil look?
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water contamination. The differential still looks ok so I would drain it out and wash it out with some of the new fluid and then refill. Did you drive through high water or something?
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water contamination for sure. I would say that if the diff in the back is like this it would be safe to change out the whole drivetrain. and i would suggest any good quality low price fluids for refill, run them out a few miles to flush the drive train. if the flush fluids drain out dirty flush again, if not fill and forget about them for awhile.
kc
kc
How can you tell that it is water contamination?
If the gear oil has that "Light Gray" appearance, is that the tell tale sign of water contamination?
Could the water be entering through the wheel bearing seal?
Inquiring minds would like to know how to spot this contamination and how could water be entering to cause the gear oil to turn a gray color with metal.
Thanks.
If the gear oil has that "Light Gray" appearance, is that the tell tale sign of water contamination?
Could the water be entering through the wheel bearing seal?
Inquiring minds would like to know how to spot this contamination and how could water be entering to cause the gear oil to turn a gray color with metal.
Thanks.
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I know that water can enter into the differential of my T4R through the breather cap on the differential housing.
The rear axle on the T4R has a little breather cap (with-OUT the hose) on top of the axle. The silver cap acts as a one-way valve. When the axle housing gets hot and pressure builds up, the cap pops open, releasing the gas and then closes down to prevent water from getting in.
HOWEVER, in theory, this cap can malfunction, especially when you have mud/dirt sticking to it. This can happen if you off-road often or cross streams often or just drive in a lot of rain. And if it malfunctions, then water/mud can get into the differential housing. I think that on the T4R has these pressure release caps on both the front and rear differentials. FWIU.....There is a mod that can be done to remedy this problem.
The rear axle on the T4R has a little breather cap (with-OUT the hose) on top of the axle. The silver cap acts as a one-way valve. When the axle housing gets hot and pressure builds up, the cap pops open, releasing the gas and then closes down to prevent water from getting in.
HOWEVER, in theory, this cap can malfunction, especially when you have mud/dirt sticking to it. This can happen if you off-road often or cross streams often or just drive in a lot of rain. And if it malfunctions, then water/mud can get into the differential housing. I think that on the T4R has these pressure release caps on both the front and rear differentials. FWIU.....There is a mod that can be done to remedy this problem.
Originally Posted By: 1 FMF
75,000 miles on factory fill GM purple smelling gear lube.
What year and what type vehicle? It looks like a 14 bolt, so I am guessing it is a heavy duty truck.
There was a blue colored 75w-90 in my 2001 GMC truck.
As others have said, it looks like water contamination.
Did you buy the truck from someone who had a boat?
People who have boats on a trailer usually put the rear axle under water when they back their trailer into the water. One of the most common mistakes is to back into the water immediately after a long drive. What happens is the rear end gets warm/hot and the air inside expands. When the put the hot axle in the water it almost instantly cools down and pulls water in through the axle seals and axle vent. The seals are meant to keep the fluid inside the axle, and not really to keep something out. Your brake calipers/cylinders would do the same thing if you put the caliper under water before letting it cool down. Since your rear end looks like it was contaminated with water, I suggest you flush your brake system also, just in case the previous owner had a boat. It wouldn't hurt to do it anyways. If you have a 4 wheel drive, check the front differential as well. 75,000 is a good time to change it. I do mine between 30,000 and 50,000 miles.
75,000 miles on factory fill GM purple smelling gear lube.
What year and what type vehicle? It looks like a 14 bolt, so I am guessing it is a heavy duty truck.
There was a blue colored 75w-90 in my 2001 GMC truck.
As others have said, it looks like water contamination.
Did you buy the truck from someone who had a boat?
People who have boats on a trailer usually put the rear axle under water when they back their trailer into the water. One of the most common mistakes is to back into the water immediately after a long drive. What happens is the rear end gets warm/hot and the air inside expands. When the put the hot axle in the water it almost instantly cools down and pulls water in through the axle seals and axle vent. The seals are meant to keep the fluid inside the axle, and not really to keep something out. Your brake calipers/cylinders would do the same thing if you put the caliper under water before letting it cool down. Since your rear end looks like it was contaminated with water, I suggest you flush your brake system also, just in case the previous owner had a boat. It wouldn't hurt to do it anyways. If you have a 4 wheel drive, check the front differential as well. 75,000 is a good time to change it. I do mine between 30,000 and 50,000 miles.
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Originally Posted By: mongo161
How can you tell that it is water contamination?
If the gear oil has that "Light Gray" appearance, is that the tell tale sign of water contamination?
Could the water be entering through the wheel bearing seal?
Inquiring minds would like to know how to spot this contamination and how could water be entering to cause the gear oil to turn a gray color with metal.
Thanks.
The oil will look milky grey and gooey. it also wont feel like oil. It is hard to describe the difference in feel on an internet forum, but if you had new gear oil and the contaminated stuff you should be able to easily feel the difference. That also depends on how much contamination is present.
Put it in a clear glass or plastic container and let it sit for a few days. You should see the water and oil start to separate.
Yes water can come in through the axle seals. (see my other post above this one)
I a not claiming to be an expert on water contaminated gear oil, but I have seen some water contaminated gear oil and it looked like that.
As someone already wrote, I suggest you find some cheap 75w-90 gear oil (stalube) and run it for a few days then drain and refill with some good stuff like Amsoil Severe Gear. You could also try to flush with really cheap 85w-90 gear oil. I don't think it would hurt anything to run a non-synthetic in your differential. the above is assuming your owners manual says to use 75w-90 gear oil otherwise use what they recommend.
How can you tell that it is water contamination?
If the gear oil has that "Light Gray" appearance, is that the tell tale sign of water contamination?
Could the water be entering through the wheel bearing seal?
Inquiring minds would like to know how to spot this contamination and how could water be entering to cause the gear oil to turn a gray color with metal.
Thanks.
The oil will look milky grey and gooey. it also wont feel like oil. It is hard to describe the difference in feel on an internet forum, but if you had new gear oil and the contaminated stuff you should be able to easily feel the difference. That also depends on how much contamination is present.
Put it in a clear glass or plastic container and let it sit for a few days. You should see the water and oil start to separate.
Yes water can come in through the axle seals. (see my other post above this one)
I a not claiming to be an expert on water contaminated gear oil, but I have seen some water contaminated gear oil and it looked like that.
As someone already wrote, I suggest you find some cheap 75w-90 gear oil (stalube) and run it for a few days then drain and refill with some good stuff like Amsoil Severe Gear. You could also try to flush with really cheap 85w-90 gear oil. I don't think it would hurt anything to run a non-synthetic in your differential. the above is assuming your owners manual says to use 75w-90 gear oil otherwise use what they recommend.
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i don't know the history of the truck other than it's out of VT and had only one original owner.
It's a GMC sierra 2500hd with the 8.1L and allison trans, crew cab, 6.5' bed. running adv auto 80w90 in the front and rear diffs now. It's the big 11.5" AAM rear with 4.10 ratio, took 4+ quarts of oil.
It's a GMC sierra 2500hd with the 8.1L and allison trans, crew cab, 6.5' bed. running adv auto 80w90 in the front and rear diffs now. It's the big 11.5" AAM rear with 4.10 ratio, took 4+ quarts of oil.
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