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Discussion Starter · #1 ·
Hi everyone. Im new and look forward to exchanging information. So I changed the rear diff oil on my 2012 Frontier pro4X and the oil was like chocolate milk. I assume this is water but I dont do any off roading or driving in water. Any idea what has caused this. The reason I drained it is because it started making a humming noise at around 60-80km/hour and stops when I take my foot off the gas. There was only a few tiny metal flakes on the drain plug magnet.
 

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Welcome to the forum! A few metal flakes on the drain plug is no big deal and pretty standard. The chocolate milk however is not.

Have you owned the truck since new? If not there's a chance that the previous owner got into some water? Have you done the axle vent mod yet? If not is the axle vent there and fully intact/not broken off? Are there any visible leaks? Cuz if water is getting in then fluid can get out. It would be good to fix any leaks while you're on it.

If there's no leaks and you don't go into water then a fluid change might remedy the problem.
 

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I'd do the vent mod (find via search) and maybe change oil again after 500 miles as it is easy to do.

If you get lucky the sound may go away and bearings in there may be ok.
 

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Discussion Starter · #4 ·
Welcome to the forum! A few metal flakes on the drain plug is no big deal and pretty standard. The chocolate milk however is not.

Have you owned the truck since new? If not there's a chance that the previous owner got into some water? Have you done the axle vent mod yet? If not is the axle vent there and fully intact/not broken off? Are there any visible leaks? Cuz if water is getting in then fluid can get out. It would be good to fix any leaks while you're on it.

If there's no leaks and you don't go into water then a fluid change might remedy the problem.
Im the original owner. Yes I relocated the vent by extending the tubing up into the tail light and put a filter on the end. It was a vent kit I purchased last year. I dont see any visible leaks except when I checked my back breaks I did notice the shoes were damp likely with oil. I was told these trucks sweat oil at the seal. Apart from that no leaks. I replaced the oil twice to help flush out the contaminated oil. I think the noise is less but not total gone. Maybe it needs a third flush. I used 75W140 as per my manual.
 

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Discussion Starter · #5 ·
I'd do the vent mod (find via search) and maybe change oil again after 500 miles as it is easy to do.

If you get lucky the sound may go away and bearings in there may be ok.
I did the vent mod last year. I ran the tubing up into the tail light. Maybe it needs a third oil flush after driving it for a while.
 

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Im the original owner. Yes I relocated the vent by extending the tubing up into the tail light and put a filter on the end. It was a vent kit I purchased last year. I dont see any visible leaks except when I checked my back breaks I did notice the shoes were damp likely with oil. I was told these trucks sweat oil at the seal. Apart from that no leaks. I replaced the oil twice to help flush out the contaminated oil. I think the noise is less but not total gone. Maybe it needs a third flush. I used 75W140 as per my manual.
If you just did the axle vent mod last year then it's very possible that your original vent failed before you did the mod cuz they are crap. From what you say about the wet rear brake pads that sounds like busted axle seals to me. It's common on these trucks because stock axle vent failure is common...and that causes the busted axle seals. Water can then easily get into leaking outer axle seals and into the diff.

All you have to do is be in water no higher than half of the tire and water will get into the axle. I do that every time I put my boat in the water or when it rains alot and some streets flood a little.
 

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Discussion Starter · #9 ·
If you just did the axle vent mod last year then it's very possible that your original vent failed before you did the mod cuz they are crap. From what you say about the wet rear brake pads that sounds like busted axle seals to me. It's common on these trucks because stock axle vent failure is common...and that causes the busted axle seals. Water can then easily get into leaking outer axle seals and into the diff.

All you have to do is be in water no higher than half of the tire and water will get into the axle. I do that every time I put my boat in the water or when it rains alot and some streets flood a little.
The vent mod was done in Nov 2019 which was only one month after the last diff oil change and I dont go into deep water. Perhaps moisture is getting in from the seals. Im going to change the oil again after about 100 miles just to be sure all the water is out. that will be its third flush and hopefully the hum will disappear.
 

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Besides repairing the seals I guess that's about all you can do for now. Of course repairing the seals can be a fairly costly repair so I would make sure my I got all the water out and that the hum is gone/diff is healthy before/if I spent the money to have those fixed.
 
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Is this the CMOD? The Chocolate Milkshake of Death. It is highly unusual for enough water to get into the differential to form CMOD. It is totally wrong to have oil splattering onto the parking brake shoes. You hear a hum coming from the differential. Your rear axle has many ailments. The really bad news is that the repair is to change out the entire rear axle. This is the NIssan way. You may find a shop to repair the componenets a la carte.
 

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Discussion Starter · #15 ·
Is this the CMOD? The Chocolate Milkshake of Death. It is highly unusual for enough water to get into the differential to form CMOD. It is totally wrong to have oil splattering onto the parking brake shoes. You hear a hum coming from the differential. Your rear axle has many ailments. The really bad news is that the repair is to change out the entire rear axle. This is the NIssan way. You may find a shop to repair the componenets a la carte.
I have a good mechanic that will be opening the cover and we’ll see what we find. I just dont understand where the water came from. I kept some old oil and I can see a clear layer on top which is strange because I was expecting the water layer on the bottom. Perhaps this oil is more dense than water.
 

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I just went thru this same situation. 2015 Frontier, 4.0 with 132,000 miles. The truck developed a hum in the rear when i would let off the gas and was coasting. I drove it that way for a while and then I finally thought to myself, "if this is a differential problem i could be causing big damage".
I had a local mechanic look at it and he said the differential was bad and needed to be replaced.
I took the truck home and took the diff cover plate off and the gears all looked fine. I did not see any missing teeth or chunks of metal. So my only guess was the axle bearings were going out.
I did not want to risk anything so i bought the complete rear differential / axle assembly from Nissan and just swapped them out. The swap was easy.
I still don't really know what was wrong with the original rear end. With the new rear end installed the humming noise went away and everything seems fine.
The old original rear end is sitting on my garage floor and i intend to do further troubleshooting and then rebuild the thing. Maybe with a locker.

I never did the vent mod. Never even heard of it until my humming noise came along and i started to research Frontier rear ends. If the axle vent is what ruined my rear end i must say i'm pretty disappointed in Nissan. When i looked at the original vent it was definitely plugged solid. I have done a lot of off roading and heavy towing with the truck in the past. A lot of mud.

I did the vent mod on the new axle.

Please keep us updated as to what happens with your truck. Very curious.
 

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Discussion Starter · #17 ·
I just went thru this same situation. 2015 Frontier, 4.0 with 132,000 miles. The truck developed a hum in the rear when i would let off the gas and was coasting. I drove it that way for a while and then I finally thought to myself, "if this is a differential problem i could be causing big damage".
I had a local mechanic look at it and he said the differential was bad and needed to be replaced.
I took the truck home and took the diff cover plate off and the gears all looked fine. I did not see any missing teeth or chunks of metal. So my only guess was the axle bearings were going out.
I did not want to risk anything so i bought the complete rear differential / axle assembly from Nissan and just swapped them out. The swap was easy.
I still don't really know what was wrong with the original rear end. With the new rear end installed the humming noise went away and everything seems fine.
The old original rear end is sitting on my garage floor and i intend to do further troubleshooting and then rebuild the thing. Maybe with a locker.

I never did the vent mod. Never even heard of it until my humming noise came along and i started to research Frontier rear ends. If the axle vent is what ruined my rear end i must say i'm pretty disappointed in Nissan. When i looked at the original vent it was definitely plugged solid. I have done a lot of off roading and heavy towing with the truck in the past. A lot of mud.

I did the vent mod on the new axle.

Please keep us updated as to what happens with your truck. Very curious.
So my mechanic informed me that parts are not even available for my differential which means I need a new one. Having said that I decided to take it to my Nissan dealer to inspect it and have them replace the diff if needed. I negotiated an 18% discount on parts/labour when I purchased it do this will save me over $1000. In Canada a new diff is $6000 CAN$. I figure this is much cheaper than the alternative of having to buy a new truck. We’ll see in a weeks time what Nissan says.
 

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So my mechanic informed me that parts are not even available for my differential which means I need a new one. Having said that I decided to take it to my Nissan dealer to inspect it and have them replace the diff if needed. I negotiated an 18% discount on parts/labour when I purchased it do this will save me over $1000. In Canada a new diff is $6000 CAN$. I figure this is much cheaper than the alternative of having to buy a new truck. We’ll see in a weeks time what Nissan says.
Wait a minute. Don't you also have bad axle seals? Changing the differential will not solve this problem.
 

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Discussion Starter · #19 ·
Wait a minute. Don't you also have bad axle seals? Changing the differential will not solve this problem.
yes I suspect the seals are gone too but If they replace the entire differential wont the new differential now have new seals. I believe they only need to reuse my brakes.When I say the differential I mean the entire rear end axels and all
 

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yes I suspect the seals are gone too but If they replace the entire differential wont the new differential now have new seals. I believe they only need to reuse my brakes.When I say the differential I mean the entire rear end axels and all
The differential is the mechanical gears and bearings in the pumpkin. The entire axle is called the axle which contains said pumpkin. If you changed out the axle, you are good to go.
 
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