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Discussion Starter · #1 ·
Hey all, new to the community and have been searching the forums but can’t find my exact problem. So I hear some grinding going on, I thought brakes, but no they’re fine. Take it to a local shop, they say I need to replace the rear differential. I ask them if there is any shavings in the fluid and they bring me in the garage to see. When the filler plug is popped the fluid spurts out, then drips and no shavings or debris. I asked them to replace the plug and put some more fluid in. On the way home, no problems till about 5 minutes away (15 minutes from home) it starts grinding again. I am thinking it is just a seal problem (85k miles). I am an amateur when it comes to vehicles, basic maintenance brakes, oil, cooling system, filters, etc. This is above my knowledge but I do not believe I need a new differential. Any help is appreciated. Thanks.
 

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Removing the plug for a visual look for shavings is a step in the right direction - but the entire differential needs to be pulled apart to see if theres some metal bits in the bottom. Either that - or drain it and get a pen light camera that can look down in there. I'm going to assume your the second owner ? Was there anything leading up to the grinding noise you can think of ? And hey - welcome to the forum ! ( sorry that your first post is a grinding gear problem ! )
 

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Discussion Starter · #3 ·
I am the original driver of the vehicle (was company owned). I bought the Xterra because I love this truck/suv. AFAIK the normal maintenance was done but not anything extra. There is another local guy I am planning to take it to, but I just wanted to affirm that it just doesn’t “need to be replaced with a new one”. There was a minor grinding sound before it went very bad. Stopped driving her until I got better knowledge of the situation. Should there be enough air pressure in there to squirt out fluid then go to a solid drain? Thanks!
 

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Well... it might need to be replaced w/ a new one. Totally depends on those internal gears - typically it's the spider gears inside the carrier that go out . There are shops that can replace just the gears, but with the mount of labor + parts involved, yes, a lot of folks would just swap out the entire rearaxle. Your Pro-4X - if it's a manual transmission - is set at the factory @ a gear ratio of 3.69 : 1 and it's highly sought after. Can be pricey because it's the ratio a LOT of Xterra owners wanna install. ( I'm one of them!) If it's a automatic transmission the gears are set @ 3.36 : 1 and a bit easier to find. Why Nissan did this is beyond me. It just is.

You could really find a ton of info on this site. Be careful, it's kind of like Alice tumbling down a rabbit hole.
 

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The temptation may be to open the differential and inspect it yourself.
However, differential problems can be difficult to identify without the knowledge of what you should be looking for. I would suggest finding a shop which specializes in differentials and have them provide a second opinion.
 

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I am the original driver of the vehicle (was company owned). I bought the Xterra because I love this truck/suv. AFAIK the normal maintenance was done but not anything extra. There is another local guy I am planning to take it to, but I just wanted to affirm that it just doesn’t “need to be replaced with a new one”. There was a minor grinding sound before it went very bad. Stopped driving her until I got better knowledge of the situation. Should there be enough air pressure in there to squirt out fluid then go to a solid drain? Thanks!
There shouldn't be any pressure in there except for gravity, as long as the differential breather is working. Sometimes they get clogged, and one of the simplest, cheapest mods you can do is routing a breather hose up higher to prevent water ingestion if you go through any deep water or mud. See here:

If your differential cannot breathe, as the fluid heats up it creates pressure that can over time blow your axle or pinion seals.

Back on topic, as others have suggested, get a second opinion from another shop. A grinding sound from the differential sound like it could be bad news, but maybe have the first shop explain in a little more detail why they feel you need to throw a very expensive new part on there.
 

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Discussion Starter · #7 ·
Thanks for the info and the welcome! Hope to be on here for more than problems :(
 

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Well... it might need to be replaced w/ a new one. Totally depends on those internal gears - typically it's the spider gears inside the carrier that go out . There are shops that can replace just the gears, but with the mount of labor + parts involved, yes, a lot of folks would just swap out the entire rearaxle. Your Pro-4X - if it's a manual transmission - is set at the factory @ a gear ratio of 3.69 : 1 and it's highly sought after. Can be pricey because it's the ratio a LOT of Xterra owners wanna install. ( I'm one of them!) If it's a automatic transmission the gears are set @ 3.36 : 1 and a bit easier to find. Why Nissan did this is beyond me. It just is.

You could really find a ton of info on this site. Be careful, it's kind of like Alice tumbling down a rabbit hole.
Because the overdrive ratio is different between the two transmissions. They both cruise down the highway at about the same RPM in overdrive. The automatic has a little overdrive, .85:1 but the manual has a taller overdrive, .75:1 I think.

The first gear in the automatic is also extra low. When this transmission was released (can't compare it to the modern 8-10 speeds out today) the 3.5:1 first gear was crazy low. Most everything else was only 2.8:1 industry wide. This is what lets the transmission work with what are normally very tall gears. A torque convertor in front of 3.5 gears, no wonder the driveline is so stout.
 
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